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Heat stress in livestock—The role of the gut in its aetiology and a potential role for betaine in its alleviation
Abstract
107 Summary A new paradigm for the aetiology of heat stroke in humans has emerged recently, which invokes the possibility of novel approaches to the treatment and prevention of heat stress in livestock species. Exposure to heat results in redistribution of blood to the periphery and compensatory reduction in the blood supply to the gut, which damages cells lining the gut, permitting endotoxin to enter the body. Endotoxin causes tissue damage and an acute–phase immune response. When blood supply resumes, reactive oxygen species and cytokines are released and cause multiple organ injury. Available evidence from livestock species is concordant with this paradigm. The possibility that the integrity of the gut lining is critical to resilience against hyperthermia has great significance for livestock species because energy–dense production diets are known to damage the gut lining. Betaine would impact beneficially at several critical points in the progression of thermally induced tissue damage. These include amelioration of damage to gut and liver tissue, and protection against the effects of endotoxin. It is proposed that administration of betaine to livestock would not only ameliorate losses in heat–stressed animals but also render them more resilient to heat.
... Dietary agents may include the antidiabetic compounds such as chromium and thiazolidinediones as well as the osmolyte betaine (Dunshea et al. 2008). There have been fewer studies in ruminants than in pigs and poultry, but there is some evidence that dietary betaine can reduce heat stress and improve feed intake and growth performance in beef cattle (Cronje 2005; Loxton et al. 2007) and sheep (DiGiacomo 2011). Also, there is now evidence that insulin resistance causes oxidative damage and that supranutritonal supplementation with anti-oxidants may mitigate against heat stress, at least in sheep (Chauhan et al. 2012). ...
... the maintenance energy requirement of the animal (Schrama et al. 2003; Suster et al. 2004) by reducing the need for sodium/potassium pumping to maintain cellular osmolarity. Dietary betaine can improve the integrity of gut mucosal cells and reduce the severity of some enteric infections in poultry (Matthews and Southern 2000; Klasing et al. 2002). Cronje (2005) has suggested that heat stress and its manifestations is a disease of the gut and that dietary betaine may assist by improving gut integrity. There have been fewer studies in ruminants than in pigs and poultry, but there is some evidence that dietary betaine can reduce heat stress and improve feed intake and growth performance in beef c ...
... Cronje (2005) has suggested that heat stress and its manifestations is a disease of the gut and that dietary betaine may assist by improving gut integrity. There have been fewer studies in ruminants than in pigs and poultry, but there is some evidence that dietary betaine can reduce heat stress and improve feed intake and growth performance in beef cattle (Cronje 2005; Loxton et al. 2007). Importantly, albeit with small numbers, Loxton et al. (2007) found that dietary betaine supplementation reduced the incidence of heat toughening (an indication of heats stress or inability to dissipate heat) from 5/6 carcasses to 1/7 carcasses (c 2 = 6.8, ...
Heat stress negatively impacts on a variety of animal production parameters. Advances in management strategies have alleviated some of the negative impacts of thermal stress on farm animals, but production continues to markedly decrease during heat events in summer, particularly in dairy cattle. In this paper we introduce a Dairy Risk Assessment Program (DRAP). The DRAP is a user-friendly software package designed to assist users in predicting heat loads in dairy cow herds. DRAP was developed over three Australian summers using climatic data (temperature, humidity, solar radiation and wind speed), cow production data (milk yield and milk quality), and physiological data (respiration rate and body temperature). The data were used to develop mathematical algorithms which can predict animal response to climatic variables. This software package is designed to be used by the dairy industry to better manage cows during times of elevated environmental temperatures by equipping producers, managers, and dairy industry personnel with Dairy Heat Load Index (DHLI) values which were calculated based upon site information, stock characteristics, management practices, and mitigation variables specific to their dairy production unit. When a heat event is imminent producers can then introduce management strategies such as providing shade or additional water troughs or implementation of nutritional strategies. Some of these nutritional strategies include dietary chromium picolinate, betaine and antioxidant supplementation or altering the rate of starch fermentation. These nutritional strategies are discussed at some length in this paper.
... Heat stress in the absence of endophyte alkaloids Cronje (2005) has recently reviewed the literature on heat stress and has firmly argued for the application of a new paradigm in humans and domestic animals "that places damage to the tissues of the gut as the pivot through which the adverse effects of heat load are promulgated". The cascade of events includes ischemic damage to the gut wall permitting entry of endotoxin; endotoxin initiation of reperfusion injury; endotoxin precipitation of septic shock and multiple organ injury. ...
... The cascade of events includes ischemic damage to the gut wall permitting entry of endotoxin; endotoxin initiation of reperfusion injury; endotoxin precipitation of septic shock and multiple organ injury. The body responds to damage to critical protein molecules by producing heat shock proteins (HSPS) that stabilise protein structure and remove the effects of denaturation and reduce the effects of inflammatory cytokines (see Cronje 2005). ...
Papers by 12 Agricultural and Veterinary Research Scientists on impact including ill-thrift and sub-clinical production losses, research needs, research conducted in New Zealand and USA (tall fescue toxicosis), and systems biology of the grass-endophyte association. Illustrated Presentations and discussions from a National Symposium held at Attwood, Victoria, 18 March 2005. 98 pages.
Editors: KFM Reed, SW Page, IJ Lean
... This shows the less severity of nutritional stress in inducing HSP70 expression as compared to heat stress. There are reports suggesting expression of HSP in the rumen (Cronje 2005). Cronje (2005) attributed this HSP expression in the rumen to redistribution of blood to the periphery and compensatory reduction in the blood supply to the gut, which damages cells lining the gut, permitting endotoxin to enter the body. ...
... There are reports suggesting expression of HSP in the rumen (Cronje 2005). Cronje (2005) attributed this HSP expression in the rumen to redistribution of blood to the periphery and compensatory reduction in the blood supply to the gut, which damages cells lining the gut, permitting endotoxin to enter the body. These consequences are more severe in CS group since the rumen is populated with bacteria that are predominantly of the endotoxin–producing gram–negative type and since two stresses are impacting simultaneously the CS group, the endotoxin production would be more in this group leading to more HSP70 expression (Cronje 2005) as compared to NS group. ...
A study was conducted to assess the impact of heat stress, nutritional stress and combined stresses (heat and nutritional stress) on rumen fermentation characteristics, histopathology of rumen and rumen HSP70 gene expression in goats. Twenty four adult Osmanabadi bucks were divided into four groups, C (n=6; control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined stress). The study was conducted for a period of 45 days. The C and HS bucks had ad libitum access to their feed while NS and CS bucks were subjected to restricted feed (30% intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to heat stress in an outside environment. Both feed intake and body weight were significantly (p < 0.01) lower in CS and NS groups. The carboxy methyl cellulase activities-extracellular, intracellular and total activity in the rumen fluid differed significantly (p < 0.01) between the groups. The highest concentration of ammonia nitrogen (p < 0.05) was recorded in C while the lowest in the CS group. The concentration of total nitrogen and trichloroacetic acid precipitable N, propionic acid, butyric acid, and valeric acid was lower (p < 0.01) in the restricted fed (NS and CS) bucks as compared to ad libitum fed groups (C and HS). Further, the ratio of acetate to propionate (A: P ratio) was also significantly (p < 0.01) higher in CS and NS groups. The higher expression of rumen heat shock protein 70 (HSP70) mRNA was observed in CS goats. The histopathological section of rumen revealed a reduction in the length of rumen villi and thickness in CS, whereas rumen keratinization was highest in the CS group. From the study it can be concluded that when two stresses occur simultaneously, they may have severe impact on rumen fermentation characteristics of bucks.
... The upregulated gene LIPG possesses both phospholipase and triglyceride lipase roles that mainly hydrolyzes the phospholipids part of lipoproteins and are generally involved in glycolipid metabolism [38]. Chickens under HS conditions endure visceral ischemia along with feed intake reduction resulting in severe nutrient scarcity at the cellular level [39]. The degradation and catabolism of lipoproteins and amino acids may be a potential source for producing energy and nutrient molecules in the ileum cells of chickens reared under chronic HS. ...
Eimeria (E.) maxima parasite infects chickens’ midgut disrupting the jejunal and ileal mucosa causing high morbidity and mortality. Heat stress (HS) is a seasonal stressor that impacts biological functions leading to poor performance. This study elucidates how HS, E. maxima infection, and their combination affect the ileum transcriptome. Two-hundred and forty 2-week-old males Ross708 chickens were randomly allocated into four treatment groups: thermoneutral-control (TNc), thermoneutral-infected (TNi), heat-stress control (HSc), and heat stress-infected (HSi), with 6 replicates each of 10 birds. Infected groups received 200x10³ sporulated E. maxima oocysts/bird, and heat-treated groups were raised at 35°C. At 6-day post-treatment, ileums of five randomly selected chickens per group were sampled, RNA was extracted and sequenced. A total of 413, 3377, 1908, and 2304 DEGs were identified when applying the comparisons: TNc vs HSc, TNc vs TNi, HSi vs HSc, and TNi vs HSi, respectively, at cutoff ≥1.2-fold change (FDR: q<0.05). HSc vs TNc showed upregulation of lipid metabolic pathways and degradation/metabolism of multiple amino acids; and downregulation of most immune-related and protein synthesis pathways. TNc vs TNi displayed upregulation of most of immune-associated pathways and eukaryotic mRNA maturation pathways; and downregulation of fatty acid metabolism and multiple amino acid metabolism pathways including tryptophan. Comparing HSi versus HSc and TNi revealed that combining the two stressors restored the expression of some cellular functions, e.g., oxidative phosphorylation and protein synthesis; and downregulate immune response pathways associated with E. maxima infection. During E. maxima infection under HS the calcium signaling pathway was downregulated, including genes responsible for increasing the cytoplasmic calcium concentration; and tryptophan metabolism was upregulated, including genes that contribute to catabolizing tryptophan through serotonin and indole pathways; which might result in reducing the cytoplasmic pool of nutrients and calcium available for the parasite to scavenge and consequently might affect the parasite’s reproductive ability.
... Aynı zamanda sıcaklık stresi altındaki hayvanlarda çeşitli faydalı etkiler gösterebilen bir ozmotik basıncı düzenleyici ve metil donörüdür. 62 Betain takviyesi hem sağlıklı hem de koksidiyozla enfekte olmuş kanatlılarda bağırsak bütünlüğünü iyileştirir. 63 Betain, tavşanlarda sıcaklık stresinin kilo alımı, bağışıklık ve vücut ısısı endeksleri üzerindeki etkilerini iyileştirmiştir. ...
... lower rectal temperature was found in T2 and T3 groups as compared to control group (Table 1). The probable reason for the above may be the osmoprotective function of betaine, which may have helped the supplemented animals to retain cellular water level and total body water content compared to control animals (Cronje 2005). Betaine supplementation during heat stress or transitional stress increases hepatic metabolism and a resultant upsurge in heat production by the liver may offset the decrease in heat production in the rest of the body due to the osmoprotective effects of betaine (2019) reported that the average rectal temperature was significantly lower in betaine supplemented groups as compared to control group in buffaloes during heat stress. ...
Betaine acts as a methyl donor in metabolism and serves as an organic osmolyte, which is used by cells for protection against osmotic stress and high temperatures. The present study was carried out to investigate the effect of betaine on physiological parameters and serum electrolyte changes in postpartum lactating Murrah buffaloes during the hot-humid season. The study was performed at the Livestock Farm Complex, N.D.V.S.U., Jabalpur, in 2019. Eighteen postpartum Murrah buffaloes were randomly divided into three groups for the experiment. T1 was a control group. T2 and T3 groups were supplemented with betaine at 50 g/animal/day and 100 g/animal/day, respectively. Betaine was supplemented in the feed from day 5 postpartum and continued up to 4 months. The rectal temperature was found to be significantly lower in the T2 and T3 groups as compared to the T1 group on day 90 postpartum. The pulse rate was lower in the T2 and T3 groups as compared to the control group on day 105 postpartum. It was concluded that betaine improves serum sodium, potassium, and the chloride concentration as compared to the control group and reduces heat stress in lactating buffaloes.
... Dietary betaine can improve lean tissue deposition in pigs [12], likely due to the increased energy available from the maintenance energy savings provided when betaine functions as an osmolyte. For example, as the gut incorporates betaine and is a large energy consumer, cellular betaine usage can potentially equate to whole body energy savings of ~8% [45]. In the present experiment daily gain was greater in animals fed betaine (combined effects of 2 and 4 g/day) compared to control animals, further suggesting that betaine is energy-sparing and able to reduce metabolic heat production and spare energy; although further studies are required to examine the effects of dietary betaine supplementation on production parameters in sheep. ...
Simple Summary
Heat stress in sheep initiates physiological methods to dissipate heat that result in decreased production. This study investigated the use of a dietary supplement, the osmolyte betaine fed at two doses (2 or 4 g/day), on the physiological responses to heat in sheep. Heat exposure initiated physiological responses such as an increased rectal temperature and respiration rate as expected, while betaine supplemented at 2 g/day ameliorated these responses. Thus, dietary betaine supplementation may have beneficial effects for sheep exposed to heat.
Abstract
Heat exposure (HE) results in decreased production in ruminant species and betaine is proposed as a dietary mitigation method. Merino ewes (n = 36, 40 kg, n = 6 per group) were maintained at thermoneutral (TN, n = 18, 21 °C) or cyclical HE (n = 18, 18–43 °C) conditions for 21 days, and supplemented with either 0 (control), 2 or 4 g betaine/day. Sheep had ad libitum access to water and were pair fed such that intake of sheep on the TN treatment matched that of HE animals. Heart rate (HR), respiration rate (RR), rectal (TR) and skin temperatures (TS) were measured 3 times daily (0900 h, 1300 h, 1700 h). Plasma samples were obtained on 8 days for glucose and NEFA analysis. The HE treatment increased TR by 0.7 °C (40.1 vs. 39.4 °C for HE and TN respectively p < 0.001), TS by +1.8 °C (39.3 vs. 37.5 °C, p < 0.001) and RR by +46 breaths/min (133 vs. 87 breaths/min, p < 0.001) compared to TN. The 2 g betaine/day treatment decreased TR (39.8, 39.6 and 39.8 °C, p < 0.001), TS (38.7, 38.0 and 38.5 °C, p < 0.001) and RR (114, 102 and 116 breaths/min for control, 2 and 4 g betaine/day, p < 0.001) compared to control. Betaine supplementation decreased plasma NEFA concentrations by ~25 μM (80, 55 and 54 μmol/L for 0, 2 and 4 g/day respectively, p = 0.05). These data indicate that dietary betaine supplementation at 2 g betaine/day provides improvements in physiological responses typical of ewes exposed to heat stress and may be a beneficial supplement for the management of sheep during summer.
... Additionally, as an osmolyte, betaine can reduce energy expenditure by reducing the need for cellular ion pumps and can thus be energy sparing (Caldas et al. 1999; Craig 2004). Furthermore, the capacity of betaine to utilise osmotic gradients rather than ion pumps in intestinal tissues can decrease the energy required for Na + /K + pumps by >60% (Moeckel et al. 2002), potentially allowing whole-body energy savings of ~8% (Cronje 2005) and reducing metabolic heat production. In pigs that have the potential to use this additional energy such as those restrictively fed and/or in porcine somatrotopin-treated boars, the additional energy can be used for lean tissue deposition (Suster et al. 2004). ...
Pigs are comparatively less heat tolerant than other species of production animals, which poses challenges for stock productivity and management during seasonal heat waves that occur in summer. The issues surrounding heat and pig production are predicted to increase, based on the actions of climate change increasing the intensity, frequency and duration of heat waves. Furthermore, future growth areas of pig production are going to be in tropical regions such as Southeast Asia and Latin America. Efforts by the pig to dissipate excess body heat come at a cost to health and divert energy away from growth, compromising efficient pig production. Management of heat stress requires multiple strategies, and recent research is improving the understanding of the application of nutritional strategies to ameliorate the effects of heat stress. In particular the use of feed additives is an important, flexible and economical method to alleviate heat stress and the intensive nature of pig production lends itself to the use of additives. Some specific examples include antioxidants, betaine and chromium, which have been proved effective or being tested in mitigating some certain impacts of heat stress in pigs. The aim of this review is to summarise recent advances in the nutritional management of heat stress in pigs.
... Additionally, as an osmolyte, betaine can reduce energy expenditure by reducing the need for cellular ion pumps and can thus be energy sparing (Caldas et al. 1999; Craig 2004). Furthermore, the capacity of betaine to utilise osmotic gradients rather than ion pumps in intestinal tissues can decrease the energy required for Na + /K + pumps by >60% (Moeckel et al. 2002), potentially allowing whole-body energy savings of ~8% (Cronje 2005) and reducing metabolic heat production. In pigs that have the potential to use this additional energy such as those restrictively fed and/or in porcine somatrotopin-treated boars, the additional energy can be used for lean tissue deposition (Suster et al. 2004). ...
Pigs are comparatively less heat tolerant than other species of production animals, which poses challenges for stock productivity and management during seasonal heat waves that occur in summer. The issues surrounding heat and pig production are predicted to increase, based on the actions of climate change increasing the intensity, frequency and duration of heat waves. Furthermore, future growth areas of pig production are going to be in tropical regions such as South-east Asia and Latin America. Efforts by the pig to dissipate excess body heat come at a cost to health and divert energy away from growth, compromising efficient pig production. Management of heat stress requires multiple strategies, and recent research is improving the understanding of the application of nutritional strategies to ameliorate the effects of heat stress. In particular the use of feed additives is an important, flexible and economical method to alleviate heat stress and the intensive nature of pig production lends itself to the use of additives. Some specific examples include antioxidants, betaine and chromium, which have been proved effective or being tested in mitigating some certain impacts of heat stress in pigs. The aim of this review is to summarise recent advances in the nutritional management of heat stress in pigs.
... Insulin resistance is also known to cause oxidative damage and there is evidence in sheep that supplementing with antioxidants may help mitigate the effects of heat stress (Chauhan et al., 2012). The feeding of dietary betaine has been reported to increase DMI in heat-stressed cattle (Cronje, 2005;Loxton et al., 2007;DiGiacomo, 2011) andsheep (DiGiacomo 2011). Conversely, in a more recent study in lactating dairy cows, dietary betaine increased milk yield during a thermoneutral period but was associated with reduced feed and water intake during a period of heat stress (Hall et al., 2012). ...
In pasture-based dairy systems, supplementary feeds are used to increase dry matter intake and milk production. Historically, supplementation involved the provision of the same amount of feed (usually a grain-based concentrate feed) to each cow in the herd during milking (i.e., flat-rate feeding). The increasing availability of computerized feeding and milk monitoring technology in milking parlors, however, has led to increased interest in the potential benefits of feeding individual cows (i.e., individualized or differential feeding) different amounts and types of supplements according to one or more parameters (e.g., breeding value for milk yield, current milk yield, days in milk, body condition score, reproduction status, parity). In this review, we consider the likely benefits of individualized supplementary feeding strategies for pasture-based dairy cows fed supplements in the bail during milking. A unique feature of our review compared with earlier publications is the focus on individualized feeding strategies under practical grazing management. Previous reviews focused primarily on research undertaken in situations where cows were offered ad libitum forage, whereas we consider the likely benefits of individualized supplementary feeding strategies under rotational grazing management, wherein pasture is often restricted to all or part of a herd. The review provides compelling evidence that between-cow differences in response to concentrate supplements support the concept of individualized supplementary feeding.
Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
... With the exception of the latter, the use of such agents for livestock that produce products destined for human consumption is unlikely to be acceptable for food safety reasons. Betaine could be useful in mitigating the effects of heat stress in livestock species (Cronjé, 2005). Several studies have shown that betaine improves ADG and FCR of pigs and broilers and egg production of layers under normal climatic conditions (Ecklund at al., 2005). ...
Although there is a copious amount of information on the physiological effects of heat stress on pigs and poultry under controlled conditions, there are few estimates of the effects of heat stress under practical conditions. Accurate prediction of responses under farm conditions is limited by three main factors: (a) much of the older experimental data on responses to heat stress were derived when threshold temperatures for decreases in voluntary feed intake were poorly defined, (b) genotypes used in many trials in the past were less susceptible to heat stress than modern genotypes and (c) most experiments were conducted using constant temperature regimens. A new approach to defining the effects of heat stress on pigs and poultry that is suitable for application to practical conditions is presented. Mean daily maximum and minimum temperatures for various locations in Australia were fitted to a sine-wave cycle with a period of 24 h to estimate the duration of exposure to heat stress. Older published data were adjusted to account for more recent estimates of threshold temperatures and rates of decreases in productivity. Adjusted threshold temperatures and rates of productivity decreases were applied to estimates of the duration of exposure to heat stress for various locations and months of the year to derive estimates of the effects of heat stress on growing and lactating pigs, broilers and layers under Australian farm conditions.
... In addition to improving health, betaine may also improve sport performance. Since betaine is an osmolyte that protects cells under stress [6,7], initial studies on the potential ergogenicity focused on the acute effects of betaine ingestion on performance in the heat [8,9]. In one study, subjects ran in a heated environment (31.1°C) for 75 minutes at 65% of VO 2 max followed by a performance run at 84% of VO 2 max to volitional exhaustion [8]. ...
To examine the effect of betaine supplementation on cycling sprint performance.
Sixteen recreationally active subjects (7 females and 9 males) completed three sprint tests, each consisting of four 12 sec efforts against a resistance equal to 5.5% of body weight; efforts were separated by 2.5 min of cycling at zero resistance. Test one established baseline; test two and three were preceded by seven days of daily consumption of 591 ml of a carbohydrate-electrolyte beverage as a placebo or a carbohydrate-electrolyte beverage containing 0.42% betaine (approximately 2.5 grams of betaine a day); half the beverage was consumed in the morning and the other half in the afternoon. We used a double blind random order cross-over design; there was a 3 wk washout between trials two and three. Average and maximum peak and mean power were analyzed with one-way repeated measures ANOVA and, where indicated, a Student Newman-Keuls.
Compared to baseline, betaine ingestion increased average peak power (6.4%; p < 0.001), maximum peak power (5.7%; p < 0.001), average mean power (5.4%; p = 0.004), and maximum mean power (4.4%; p = 0.004) for all subjects combined. Compared to placebo, betaine ingestion significantly increased average peak power (3.4%; p = 0.026), maximum peak power max (3.8%; p = 0.007), average mean power (3.3%; p = 0.034), and maximum mean power (3.5%; p = 0.011) for all subjects combined. There were no differences between the placebo and baseline trials.
One week of betaine ingestion improved cycling sprint power in recreationally active males and females.
... From the non-significant differences in body fluid related variables between the B and P trials, due to the experimental controls for hydration employed in this study, it seems that betaine's established role as an osmoprotectant [2,7,8] was not a likely candidate for any ergogenicity. This does not, however, minimize the potential role of betaine given the intensity of the REC, as organic osmolytes have been shown to accumulate in cells under varying stressful conditions to help maintain biochemical function161718 . Additionally, plasma glucose and lactate results in this study indicate that betaine was either 1) not acting through glucose or lactate processing, or 2) the pre-existing differences amongTable 1 Total number of repetitions to fatigue in the back squat during the two days before and after supplementation (n = 12) subjects masked any betaine effects on these dependent variables. ...
Abstract
Background
We investigated the ergogenic effects of betaine (B) supplementation on strength and power performance.
Methods
Twelve men (mean ± SD age, 21 ± 3 yr; mass, 79.1 ± 10.7 kg) with a minimum of 3 months resistance training completed two 14-day experimental trials separated by a 14-day washout period, in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of twice daily B or placebo (P) supplementation, subjects completed two consecutive days (D1 and D2) of a standardized high intensity strength/power resistance exercise challenge (REC). Performance included bench, squat, and jump tests.
Results
Following 14-days of B supplementation, D1 and D2 bench throw power (1779 ± 90 and 1788 ± 34 W, respectively) and isometric bench press force (2922 ± 297 and 2503 ± 28 N, respectively) were increased (p < 0.05) during REC compared to pre-supplementation values (1534 ± 30 and 1498 ± 29 W, respectively; 2345 ± 64 and 2423 ± 84 N, respectively) and corresponding P values (1374 ± 128 and 1523 ± 39 W; 2175 ± 92 and 2128 ± 56 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p < 0.05) on D1 and D2 following B supplementation. However, there were no differences in jump squat power or the number of bench press or squat repetitions.
Conclusion
B supplementation increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups.
... From the non-significant differences in body fluid related variables between the B and P trials, due to the experimental controls for hydration employed in this study, it seems that betaine's established role as an osmoprotectant [2,7,8] was not a likely candidate for any ergogenicity. This does not, however, minimize the potential role of betaine given the intensity of the REC, as organic osmolytes have been shown to accumulate in cells under varying stressful conditions to help maintain biochemical function161718 . Additionally, plasma glucose and lactate results in this study indicate that betaine was either 1) not acting through glucose or lactate processing, or 2) the pre-existing differences amongTable 1 Total number of repetitions to fatigue in the back squat during the two days before and after supplementation (n = 12) subjects masked any betaine effects on these dependent variables. ...
We investigated the ergogenic effects of betaine (B) supplementation on strength and power performance.
Twelve men (mean +/- SD age, 21 +/- 3 yr; mass, 79.1 +/- 10.7 kg) with a minimum of 3 months resistance training completed two 14-day experimental trials separated by a 14-day washout period, in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of twice daily B or placebo (P) supplementation, subjects completed two consecutive days (D1 and D2) of a standardized high intensity strength/power resistance exercise challenge (REC). Performance included bench, squat, and jump tests.
Following 14-days of B supplementation, D1 and D2 bench throw power (1779 +/- 90 and 1788 +/- 34 W, respectively) and isometric bench press force (2922 +/- 297 and 2503 +/- 28 N, respectively) were increased (p < 0.05) during REC compared to pre-supplementation values (1534 +/- 30 and 1498 +/- 29 W, respectively; 2345 +/- 64 and 2423 +/- 84 N, respectively) and corresponding P values (1374 +/- 128 and 1523 +/- 39 W; 2175 +/- 92 and 2128 +/- 56 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p < 0.05) on D1 and D2 following B supplementation. However, there were no differences in jump squat power or the number of bench press or squat repetitions.
B supplementation increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups.
Heat stress (HS) reduces production and efficiency in almost every metric of the dairy operation, and it thus compromises profitability and sustainability. If the magnitude of HS progresses, it can become lethal. Death can occur acutely or days following the heat load, even if environmental conditions have become nonstressful. Consequently, lethal heat stress (LHS) is often difficult to identify and almost always misdiagnosed. The precise mechanisms of death when dairy cows succumb to LHS has not been fully elucidated or documented, but the pathophysiology of LHS appears to be conserved among several species. The unique digestive physiology of ruminants adds additional layers of complexity that contribute to failure of multiple systems involved with LHS. Consequently, the ostensible etiology and pathogenesis of LHS described herein is extended from the physiological adaptations cows use to survive HS and pertinent pathology extrapolated from other species. The multifactorial causes of death likely involve dysfunction and imbalance of several interdependent systems as follows: (1) electrolyte dyshomeostasis, (2) unstable blood pH, (3) gastrointestinal tract hyperpermeability, (4) sepsis, (5) severe immune activation-induced inflammation, (6) disseminated intravascular hypercoagulation, (7) systemic endothelial permeability, (8) multiple organ failure, and (9) circulatory failure. Having a better understanding of the mechanisms of LHS will improve diagnosis, enable a more accurate prognosis, and provide insight into strategies aimed at preventing dairy cow mortality and morbidity.
Heat stress (HS) has been implicated in several negative impacts on farm animal welfare and their production. Some of the negative impacts of HS on farm animals have been alleviated by the advances in management strategies. Despite all the advances, HS continues to impact farm animal production during summer heat events, particularly in dairy. Implementation of management strategies, such as providing shade or additional water troughs, and/or nutritional strategies could help the producers when a heat event is imminent. Some of the nutritional strategies that could be utilised include antioxidant supplementation, dietary Cr, betaine and altering the rate of starch fermentation, which have been demonstrated to decrease HS under some circumstances. These nutritional strategies are discussed in this chapter.KeywordsAntioxidantDairy cattleHeat stressNutritional strategiesStarch fermentation
Previous studies have suggested that feeding slowly fermentable grains might improve heat-tolerance in ruminants, due to increased post-rumen starch digestion and a reduction in the heat increment of feeding. During heat stress gastrointestinal function may be compromised which could impact on the site and extent of digestion. To characterize the in vitro rumen starch and DM disappearance of corn, wheat, and 3% NaOH-treated wheat grains, grain samples were incubated during 0, 5, 8, and 24 h at 39 °C in buffered rumen fluid. Then faecal pH and whole tract apparent starch, DM, and organic matter (OM) digestibility were determined in wethers fed, with either corn (CD), wheat (WD) or 3% NaOH- treated wheat (TWD) based diets during heat stress in two experiments. In experiment 1, 22 wethers were fed either CD or WD (n = 11 per diet) during three different stages in climate controlled rooms: stage 1 (TNFR), 7 days of thermoneutral conditions 18–21 °C and 40–50% relative humidity) and 1.3 times maintenance feed intake; stage 2 (HSFR), 7 days of heat stress (28–38 °C and 30–50% relative humidity) and feed intake as TNFR; and stage 3 (HSFU), 7 days of heat stress as in HSFR stage and 1.5 times maintenance feed intake. In experiment 2, 31 wethers were fed either CD (n = 10), WD (n = 10) or TWD (n = 11) during three different stages with the same temperature and relative humidity regimes as experiment 1, however during TNFR and HSFR stages wethers received 1.7 times maintenance feed intake while in HSFU stage wethers received 2 times maintenance feed intake. After 24 h of incubation, untreated wheat had the fastest rate of starch and DM disappearance followed by 3% NaOH-treated wheat and corn grain (P < 0.001). Wethers fed CD had lower apparent starch (P < 0.001) and higher DM (P < 0.001) and OM (P < 0.001) digestibility than those fed WD, which was associated with lower faecal pH (P < 0.001) and higher faecal starch content (P < 0.001) than wheat diets. 3% NaOH treatment of wheat did not affect the whole tract starch digestibility of wheat being faecal pH and starch content of TWD like WD. At low feed intakes (1.3 times maintenance) there was no effect of heat stress on digestibility whereas at higher feed intakes heat stress reduced starch, OM, and DM digestibility. However, starch digestibility of TWD was similar to WD and metabolizable energy intake, DM and OM digestibility were higher. It is concluded that 3% NaOH treatment of wheat could reduce the rumen starch disappearance (in vitro condition) without reducing the whole tract starch digestibility (tested in vivo) of wheat in heat-stressed wethers. The study demonstrated the treated wheat with NaOH can be a strategy to increase OM digestibility and energy retention of wethers under heat stress.
Dairy industry plays a significant role in the agriculture sector for sustainable growth. Heat stress, on the other hand, has been proven to have a detrimental impact on dairy output in terms of growth, reproductive performance and milk production in dairy animals, especially in tropical areas. Heat stress is one of the most significant issues facing the dairy industry, as rising temperatures and humidity limit animal productivity throughout the summer, resulting in devastating economic repercussions. The purpose of this review is to gather knowledge on the effects of heat stress on dairy output and how to ameliorate them. The diversion of energy resources from the production to the adaptation pathway may be responsible for the loss in productive capacity of dairy animals, when they are exposed to heat stress. There are different approaches pertaining to relieving the adverse effects of heat stress on dairy production system. These approaches may be classified into three major categories viz. genetic, management and nutritional interventions. These approaches might help dairy animals to perform better by reducing the harmful impacts of heat stress. Appropriate shelter design, giving shade, employing sprinklers, installing cooling devices, and using fans and ventilation systems are among the management strategies. The nutritional interventions comprise ration balancing and providing essential micronutrients to improve the productive and reproductive performance. Some of the most widely used dietary measures to ensure optimal production are inclusion of protein or fat (prill fat), micronutrients antioxidants (vitamins and minerals) and some feed additives (Astaxanthin, betaine, melatonin, Chlorophytum borivilianum) in the diet. These antioxidants and feed additives can be used to attenuate the negative effects of environmental stress. Furthermore, providing adequate energy and antioxidants help to ensure optimum growth, milk production and reproduction efficiency during heat stress. This review provides an overview of the consequences of heat stress on dairy animals, emphasizes essential nutritional strategies for heat stress reduction in dairy animals, and evaluates the influence of various feed supplements on growth, productivity and physiology.
Heat stress is one of the greatest challenges for the global livestock industries as increased environmental temperature and humidity compromises animal production during summer leading to devastating economic consequences. Over the last 30 years, significant developments have been achieved in cooling and provision of shade and shelter to mitigate heat stress reducing some of the losses associated with heat stress in farm animals. However, the recent increase in the incidence of heat waves which are also becoming more severe and lasting longer, due to climate change, further accentuates the problem of heat stress. Economic losses associated with heat stress are both direct due to loss in production and animal life, and indirect due to poorer quality products as a result of poor animal health and welfare. Animal health is affected due to impaired immune responses and increased reactive oxygen species production and/or deficiency of antioxidants during heat stress leading to an imbalance between oxidant and antioxidants and resultant oxidative stress. Research over the last 20 years has achieved partial success in understanding the intricacies of heat stress impacts on oxidative stress and immune responses and developing interventions to ameliorate impacts of heat stress, improving immune responses and farm animal health. This paper reviews the body of knowledge on heat stress impacts on immune response in farm animals. The impacts of heat stress on both cell-mediated and humoral immune responses have been discussed identifying the shift in immune response from cell-mediated towards humoral response, thereby weakening the immune status of the animal. Both species and breed differences have been identified as influencing how heat stress impacts the immune status of farm animals. In addition, crosstalk signaling between the immune system and oxidative stress has been considered and the role of antioxidants as potential nutritional strategies to mitigate heat stress has been discussed.
The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP) on body temperature indices, metabolism, acute phase protein response, and production variables during heat stress (HS). Twenty multiparous lactating Holstein cows (body weight = 675 ± 12 kg; days in milk = 144 ± 5; and parity = 2.3 ± 0.1) were used in an experiment conducted in 2 replicates (10 cows/replicate). Cows were randomly assigned to 1 of 2 dietary treatments: control diet (CON; n = 10) or the CON diet supplemented with 19 g/d of SCFP (n = 10; NutriTek, Diamond V, Cedar Rapids, IA). Cows were fed their respective diets for 21 d before initiation of the study. The experiment consisted of 2 periods: thermoneutral (period 1; P1) and heat stress (period 2; P2). During P1 (4 d), cows were fed ad libitum and housed in thermoneutral conditions for collecting baseline data. During P2 (7 d), HS was artificially induced using an electric heat blanket (EHB; Thermotex Therapy Systems Ltd., Calgary, AB, Canada). Cows were fitted with the EHB for the entirety of P2. Rectal temperature, respiration rate, and skin temperature were obtained twice daily (0600 and 1800 h) during both periods. Overall, HS increased rectal temperature, skin temperature, and respiration rate (1.4°C, 4.8°C, and 54 breaths/min, respectively) relative to P1, but no dietary treatment differences were detected. Compared with P1, HS decreased dry matter intake and milk yield (36 and 26%, respectively), and the reductions were similar between dietary treatments. Relative to P1, HS increased milk fat content and milk urea nitrogen (17 and 30%, respectively) and decreased milk protein and lactose contents (7 and 1.4%, respectively). Overall, HS increased (52%) plasma cortisol concentrations of CON, but circulating cortisol did not change in SCFP-fed cows. Heat stress increased circulating lipopolysaccharide binding protein and serum amyloid A (SAA; 2- and 4-fold, respectively), and SCFP supplementation tended to decrease peak SAA (∼33%) relative to CON cows. Overall, although HS did not influence circulating white blood cells and neutrophils, SCFP increased circulating white blood cells and neutrophils by 9 and 26%, respectively, over CON in P2. In conclusion, HS initiated an acute phase protein response and feeding SCFP blunted the cortisol and SAA concentrations and altered some key leukocyte dynamics during HS.
Objectives were to determine the effects of a product containing electrolytes, osmolytes, and energetic compounds (EOEC) on body temperature indices in heat-stressed (HS) Holstein cows. Lactating cows were assigned to 1 of 2 treatments: 1) a control diet (n = 10) or 2) a control diet supplemented with 113 g/d of EOEC (n = 10; Bovine BlueLite® Pellets; TechMix LLC, Stewart, MN). The trial consisted of 2 experimental periods (P). During P1 (4 d), cows were fed their respective treatments and housed in thermoneutral conditions. During P2 (4 d), HS was artificially induced using an electric heat blanket (EHB). Overall, HS markedly increased vaginal temperature (Tv), rectal temperature (Tr), skin temperature (Ts), and respiration rate (RR) (P < .01). There were no dietary treatment differences in Tv, Tr, or RR; however, during P2 EOEC-supplemented cows had increased Ts (0.8 °C; P = .04). Compared to P1, HS decreased DMI and milk yield (45 and 27%, respectively, P < .01) similarly amongst treatments. Relative to P1, circulating insulin decreased (41%; P = .04) in CON cows, whereas it remained unaffected in EOEC-supplemented cows, resulting in a 2-fold increase in EOEC compared with CON-fed cows (P < .01) during P2. Relative to P1, HS increased circulating non-esterified fatty acids (NEFA; 63%; P < .01). During P2, there tended to be a treatment by day interaction on circulating NEFA, as concentrations decreased from d 2 to 4 of P2 in EOEC-fed cows but continued to increase in CON cows. In summary, feeding EOEC altered some key aspects of energetic metabolism and increased Ts.
Effect of betaine supplementation on physiological (RT, ST, RR and PR) responses, morphological (body length, heart girth and height at withers) parameters, stress markers (cortisol and NEFA levels), growth hormone, dry matter intake (DMI) and body weight of buffalo heifers during hot humid season under field conditions, fourteen buffalo heifers were selected and equally divided into two groups, i.e. control and treatment (supplemented betaine @25 g/animal/day over the farmers practice). Blood samples were collected at fortnightly interval from both the groups and analyzed for stress markers. THI was calculated for measuring the stress levels on buffalo heifers, which remained >76 indicated severe stress. Physiological responses were significantly lower in treatment group than control. Morphological parameters, body weight and DMI were higher in treatment than control. Plasma cortisol and NEFA levels were significantly lower, whereas plasma growth hormone was significantly higher in treatment group compared to control. ADG was significantly higher in treatment group compared to control. Positive correlation was observed between THI and stress markers, physiological responses and negatively correlated with ADG, DMI and growth hormone. Based on the results, it can be concluded that betaine acted as a potent growth promoter by lowering the levels of stress markers and enhancing the ADG and DMI of buffalo heifers.
Simple Summary
One of the common approaches to alleviating heat-stress in poultry is nutritional manipulation using herbal extracts or their derivatives to maintain the health, welfare, and performance of birds. The present study investigated the protective effect of boldo leaf extract against the harmful effects of cyclic heat stress in two broiler strains (Arbor Acres; AA and Avian-48; AV). Administration of boldo in drinking water was able to restore growth and health traits to nearly normal values. Generally, AA chicks were better able to withstand heat stress and were also more likely to utilize boldo extract than AV chicks. The use of boldo leaf extract in poultry production can assist in mitigating the effect of heat stress, improving the antioxidant defense system, and increasing productivity and profitability.
Abstract
There is increasing interest in the use of natural antioxidant supplements in poultry diets as protection against the adverse effects of heat stress. The potential protective effect of boldo (Peumus boldus molina) leaf extract, which have antioxidant activity, were investigated against the harmful effects of heat stress in two broiler strains. Arbor Acres (AA) and Avian-48 (AV) chicks were divided into thermoneutral (TN) and heat stress (HS) groups and treated with 1 g boldo leaf extract/4 L drinking water during the heat stress period. HS reduced growth performance in both strains. The phagocytic index, phagocytic activity, and eosinophil and lymphocytes counts were significantly elevated in TN and HS AV birds but not altered in AA birds. Boldo extract treatment partially eliminated the previous negative impacts of heat stress. AA chicks were better able to withstand HS than AV chicks. Serum concentrations of total lipids and cholesterol were reduced in HS birds of both strains. Malondialdehyde, superoxide dismutase, and glutathione peroxidase levels were elevated but restored with the administration of boldo leaf extract in HS birds of both strains. Economic parameters were negatively affected by HS but restored to values close to those of the control group in boldo-treated HS birds. In conclusion, the administration of boldo leaf extract in drinking water was effective in neutralizing the harmful effects of heat stress on growth performance, blood indices, and economic parameters and improved the antioxidant defense system in heat-stressed birds.
Heat stress (HS) causes oxidative stress, which compromises broiler performance and meat quality. The aim of this study was to determine whether dietary antioxidants could be used as an amelioration strategy. Seventy-two day-old-male Ross-308 chicks were exposed to either thermoneutral or cyclical heat stress conditions. Diets were either control commercial diet (CON), CON plus betaine (BET), or with a combination of betaine, selenized yeast, and vitamin E (BET + AOX). Heat stress increased the rectal temperature (p < 0.001), respiration rate (p < 0.001), decreased blood pCO2 (p = 0.002), and increased blood pH (p = 0.02), which indicated the HS broilers had respiratory alkalosis. Final body weight was decreased by HS (p < 0.001), whereas it was improved with BET (p = 0.05). Heat stress reduced cooking loss (p = 0.007) and no effect on drip loss, while BET decreased the drip loss (p = 0.01). Heat stress reduced the myofibril fragmentation index (p < 0.001) and increased thiobarbituric acid reactive substances (p < 0.001), while these were improved with the combination of BET + AOX (p = 0.003). In conclusion, BET overall improved growth rates and product quality in this small university study, whereas some additional benefits were provided by AOX on product quality in both TN and HS broilers.
Simple Summary
It is well known that the thermal environment has an integral role in maintaining the health and productivity of cattle. Although cold stress has been identified to negatively influence cattle comfort and productivity, the predominant focus herein has been describing the influence of heat stress on bovines. The impact of heat stress is particularly important due to the changing global environment. Global warming is likely to occur, however, the nature and magnitude of environmental changes, both climatic and non-climatic, are difficult to elucidate. Therefore a predominant focus on the impact of hot environments on cattle is warranted. This review provides an overview of the dynamic relationship that exists between the thermal environment and bovines.
Abstract
Heat stress and cold stress have a negative influence on cattle welfare and productivity. There have been some studies investigating the influence of cold stress on cattle, however the emphasis within this review is the influence of heat stress on cattle. The impact of hot weather on cattle is of increasing importance due to the changing global environment. Heat stress is a worldwide phenomenon that is associated with reduced animal productivity and welfare, particularly during the summer months. Animal responses to their thermal environment are extremely varied, however, it is clear that the thermal environment influences the health, productivity, and welfare of cattle. Whilst knowledge continues to be developed, managing livestock to reduce the negative impact of hot climatic conditions remains somewhat challenging. This review provides an overview of the impact of heat stress on production and reproduction in bovines.
Heat stress may adversely affect physiochemical and immune responses of livestock and alter biological functions. The comfort or thermoneutral zone for livestock, which has long been a subject of research, mainly depends on species, breed, and health. Heat stress is associated with impaired livestock productivity due to reductions in feed intake, growth rates and immunity and changes in blood constituents and biological pathways. In ruminants, elevated temperatures have deleterious consequences on protein synthesis. Exposure of ruminant animals to elevated temperatures may induce release of heat shock proteins (HSPs); HSPs usually enter the blood circulation during tissue damage and causes cell necrosis or death. Additionally, hyperthermia is associated with augmented production of cellular reactive oxygen species (ROS), which cause protein degradation and further decrease protein synthesis by preventing protein translation. Moreover, it has been suggested that high environmental temperatures lead to increased inflammatory signalling in tissues via activation of the nuclear factor kappa B (NF-κB) and tumor necrosis factor alpha (TNF-α) pathways as well as via alteration of skin colour gene (melanocortin 1 receptor (MC1R) and premelanosome protein (PMEL)) expression. Previous proteomics analyses have suggested that heat stress can reduce adenosine triphosphate (ATP) synthesis, alter gluconeogenesis precursor supply, and induce lipid accumulation in the liver with subsequent disturbance of liver structure. This review focuses on the scientific evidence regarding the impact of heat stress on immune and inflammatory responses, antioxidant status, stress biomarkers, skin colour gene (PMEL and MC1R) expression and proteomic profiles in ruminants.
A study was conducted to assess the impact of heat stress, nutritional stress and combined stresses (heat and nutritional stress) on rumen fermentation characteristics, histopathology of rumen and rumen HSP70 gene expression in goats. Twenty four adult Osmanabadi bucks were divided into four groups, C (n=6; control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined stress). The study was conducted for a period of 45 days. The C and HS bucks had ad libitum access to their feed while NS and CS bucks were subjected to restricted feed (30% intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to heat stress in an outside environment. Both feed intake and body weight were significantly (p < 0.01) lower in CS and NS groups. The carboxy methyl cellulase activities - extracellular, intracellular and total activity in the rumen fluid differed significantly (p < 0.01) between the groups. The highest concentration of ammonia nitrogen (p < 0.05) was recorded in C while the lowest in the CS group. The concentration of total nitrogen and trichloroacetic acid precipitable N, propionic acid, butyric acid, and valeric acid was lower (p < 0.01) in the restricted fed (NS and CS) bucks as compared to ad libitum fed groups (C and HS). Further, the ratio of acetate to propionate (A:P ratio) was also significantly (p < 0.01) higher in CS and NS groups. The higher expression of rumen heat shock protein 70 (HSP70) mRNA was observed in CS goats. The histopathological section of rumen revealed a reduction in the length of rumen villi and thickness in CS, whereas rumen keratinization was highest in the CS group. From the study it can be concluded that when two stresses occur simultaneously, they may have severe impact on rumen fermentation characteristics of bucks.
Heat stress is the most intriguing factor negatively influencing sheep production. Heat stress management in sheep requires multiple strategies. There are several recent research findings which help to understand the hidden intricacies of nutritional intervention ameliorating the effects of heat stress in sheep. Applications of feed additives in particular were found to be the most widely adapted methodology to alleviate heat stress in an economical way. The commonly attempted feed additives include antioxidants, betaine, chromium, insulin mimics, and manipulation of concentrates to slow fermentation. These applications were either proved to be effective, or are currently being evaluated for their potency in reversing some of the effects of heat stress in sheep. Therefore, this chapter is an attempt to review different viable nutritional strategies to ameliorate heat stress in sheep.
This study was conducted to determine and compare the effects of yeast yeast culture (YC) and vitamin E (VE) supplementation on endotoxin absorption and antioxidant status in lactating dairy goats suffering from heat stress (HS). Three first lactation Saanen dairy goats (body weight 30±1.5 kg) were surgically fitted with indwelling catheters in the portal vein, mesenteric vein and carotid artery, and were randomly assigned to a 3×3 Latin square design. Dietary treatments were the basal diet, and the basal diet supplemented with either 100 IU VE or 30 g YC. Goats were kept in temperature and humidity-controlled room at 35°C from 8:00 to 20:00 and at 24°C from 20:00 till the next morning at 8:00. The relative humidity was kept at 55%. HS increased dairy goats’ rectum temperature and respiration frequency (p
Environmental conditions influence animal production from an animal performance perspective and at the carcass level post-slaughter. High rigor temperature occurs when the animal is hyperthermic pre-slaughter, and this leads to tougher meat. Hyperthermia can result from increased environmental temperature, exercise, stress or a combination of these factors. Consumer satisfaction with beef meat is influenced by the visual and sensory traits of the product when raw and cooked, with beef consumers commonly selecting tenderness of the product as the most important quality trait. High rigor temperature leads to a reduction in carcass and eating quality. This review examines some possible metabolic causes of hyperthermia, with focus on the importance of adipose tissue metabolism and the roles of insulin and leptin. Potential strategies for the amelioration or prevention of high rigor temperature are offered, including the use of dietary supplements such as betaine and chromium, anti-diabetic agents such as thiazolidinediones, vitamin D, and magnesium (Mg) to provide stress relief.
In this in vitro study, the modified Hohenheim gas test was used to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum, when fermenting a standard pig diet with varying levels of crude protein (CP; 20, 24 and 28% CP), and supplemented with one of three fibre sources manufactured by micronization treatment. These were wheat envelopes (MWE), pea fibre (MPF) and lupine fibre (MLF). For comparison, inulin was used. As intestinal bacteria have to cope with varying osmotic conditions in their ecosystem, fermentation was performed under normal buffered and osmotic stress conditions. After 24 h of fermentation, total gas production and ammonia production were measured. In addition, the effect of MWE and inulin on short-chain fatty acid (SCFA) production and numbers of total eubacteria, Lactobacillus spp., Bifidobacterium spp., Enterobacteriaceae, Enterococcus spp., Clostridium cluster XIVa and Clostridium cluster IV, were determined using quantitative real-time PCR. Under normal buffered conditions, supplementation of MWE resulted in increased (p < 0.05) SCFA, acetic, propionic and valerianic acid production at CP levels of 20 and 28%. There was an increase (p < 0.05) in ammonia production for the micronized supplements, and for MWE an increased (p < 0.05) branched-chain proportion was observed, possibly due to higher availability of protein for fermentation which was released during the micronization process. Osmotic stress conditions reduced (p < 0.05) total gas as well as total SCFA, acetic and propionic acid production for all treatments, while cell counts were increased (p < 0.05) for Bifidobacterium spp., Enterococcus spp. and Lactobacillus spp. Under normal buffered conditions in combination with 24 and 28% CP levels, lactobacilli were increased for MWE, compared to inulin (p < 0.05). In conclusion, micronized supplements such as MWE may beneficially modulate pigs' intestinal microbiota by increasing SCFA production in addition to a selective proliferation of lactobacilli.
The current intensive indoor production system of commercial Pekin ducks never allows adequate water for swimming or wetting. Therefore, heat stress is a key factor affecting health and growth of ducks in the hot regions and season. Experiment 1 was conducted to study whether heat stress was deleterious to certain organs of ducks. Forty-one-day-old mixed-sex Pekin ducks were randomly allocated to four electrically heated battery brooders comprised of 10 ducks each. Ducks were suddenly exposed to 37 °C ambient temperature for 3 h and then slaughtered, in one brooder at 21 days and in another brooder at 49 days of age. The results showed that body weight and weight of immune organs, particularly liver markedly decreased in acute heat stress ducks compared with the control. Experiment 2 was carried out to investigate the influences of dietary L-arginine (Arg) supplement on weight and compositions of certain lymphoid organs, and growth performance in Pekin ducks, under daily cyclic hot temperature environment. A total of 151-day-old mixed-sex Pekin ducks were randomly divided into one negative control and two treatment groups, fed experimental diets supplemented with 0, 5, and 10 g L-Arginine (L-Arg)/kg to the basal diet respectively. Ducks were exposed to cyclic high temperature simulating natural summer season. The results showed that the addition of L-Arg improves feed conversion ratio (FCR) during a period of 7-week trial, as well as increases hepatic weight relative to body weight at 21 days, while decreases the hepatic water content at 49 days of age. This study indicated that the liver was more sensitive to acute heat stress, and the hepatic relative weight and chemical composition could be regulated by dietary L-Arg supplementation in Pekin ducks being reared at high ambient temperature. These beneficial effects of Arg on liver might be a cause of improved FCR.
The present review focuses on potential nutritional and physiological functions of betaine in relation to health, performance and carcass characteristics in poultry. Due to its zwitterionic structure, betaine has osmoprotective properties that aid in protecting intestinal cells and thus counteracting performance losses during heat stress and coccidiosis. Hence, betaine might be an appropriate agent in the prevention of heat stress in livestock. In addition, during coccidiosis, the efficacy of betaine appears to be related to the Eimeria species, type of coccidiostat used and the severity of infection. As this compound has methyl donor properties, betaine is involved in methylation reactions in the organism and may therefore partly substitute other methyl group donors such as methionine and choline. Due to its methyl donor and osmoprotectant functions, recent research has shown that betaine improves nutrient digestibility, growth performance and feed conversion in broiler chicks, turkeys and meat ducks. Other potential benefits of the inclusion of betaine in poultry diets are lowering carcass fat content and increasing breast meat yield which may be of interest to satisfy consumer needs.
There is evidence that dietary betaine might improve nutrient digestibilities in pigs due to its osmoprotective properties. This in vitro study was performed to assess the potential of supplemented betaine sources to affect fermentation characteristics of different carbohydrate and protein combinations, under conditions of osmotic stress. In vitro fermentation was performed by use of the modified Hohenheim gas test with pig faeces as microbial inoculum.
At the end of in vitro fermentation under osmotic stress conditions, differences (P < 0.05) in gas production, ammonia concentration, and concentration of short-chain fatty acids were observed for the different carbohydrates, while for the two proteins only differences (P < 0.05) in ammonia and short-chain fatty acid concentration were obtained. Supplementation of a native betaine source rather than addition of pure betaine increased propionic acid (P < 0.05) and butyric acid (P < 0.05) production.
These results suggest that only supplementation of a native betaine source but not of pure betaine products affects microbial fermentation under osmotic stress. Furthermore, both the carbohydrate and protein source play an important role in modifying microbial activity under osmotic stress conditions. It can also be concluded that the modified Hohenheim gas test is suitable to scrutinise fermentation activity of different assay substrates under osmotic stress.
The bacteria of the intestine have to cope with varying osmotic conditions in their ecosystem. In this in vitro study, the modified Hohenheim gas test (HGT) was used to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum, when fermenting different carbohydrates (inulin, corn starch, potato starch, cellulose, pectin), under normal buffered and osmotic stress conditions (elevated medium salinity). After 24 h of fermentation, gas, ammonia and short-chain fatty acid (SCFA) production was measured, and the cell numbers of total eubacteria, Lactobacillus spp., Bifidobacterium spp. and enterobacteria were analysed, using real-time polymerase chain reaction. There was a significant reduction in gas production after 24 h when comparing osmotic stress conditions with normal buffered conditions, and there were also differences among carbohydrates under both conditions. The content of SCFA was significantly lower when comparing osmotic stress with normal buffered conditions. Under osmotic stress, inulin and corn starch increased (p < 0.05) cell numbers of total eubacteria, while Bifidobacterium spp. and enterobacteria were higher (p < 0.05) when corn starch and pectin were fermented, respectively, in comparison to the other carbohydrates. The in vitro system of the modified HGT appears to be suitable to scrutinise effects of carbohydrates on the metabolic activity and composition of the microbial community under osmotic stress conditions, as they might occur during situations of osmotic diarrhoea.
This study was designed to evaluate the effect of heat stress on endotoxin flux across mesenteric-drained and portal-drained viscera of dairy goats. Three Saanen first lactation dairy goats were surgically fitted with indwelling catheters in the portal vein, the mesenteric vein and carotid, and were kept in thermal-neutral and then heat stress environment, for examining the effect of heat stress on endotoxin absorption and redox status. Average net absorption of endotoxin (EU/h) across mesenteric-drained viscera (MDV) and portal-drained viscera (PDV) during the whole period of heat stress increased by 279.05% and 227.92% in relation to thermo-neutral period. Plasma concentration of glutathione peroxidase (GSH-Px) and catalase (CAT) in mesenteric and portal vein, and that of superoxide dismutase (SOD) in mesenteric vein, increased significantly during heat stress. Main conclusions were: (i) net absorption of endotoxin in portal vein is mainly from non-mesenteric tissues both in heat stress and in thermo-neutral condition; (ii) heat stress may lead to the significant decrease in plasma SOD, GSH-Px, CAT flux across PDV and MDV, and the significant increase in endotoxin flux across PDV and MDV; and (iii) the increase in gastrointestinal permeability in dairy goats during heat stress may not be induced by the increase in oxidative stress.
Perennial ryegrasses are frequently infected with fungal endophyte (Neotyphodium lolii) to increase the resistance of the plant to insect damage. Unfortunately, a side effect of endophyte infection can be the production of alkaloids, including Lolitrem B and ergovaline, that produce toxic effects in animals. A significant 4.6 litre decrease in milk production in a herd of Holstein-Friesian dairy cows was associated with high concentrations of ergovaline in ryegrass silage. Simultaneously, milk SCC increased significantly over a comparable period and reproductive performance declined. Body condition score and coat condition of cows were adversely affected. Unique aspects of this Case report include; very stable production of the herd over a period of years before and after cessation of feeding silage containing high concentrations of ergovaline; the presence of high concentrations of ergovaline in the silage; and a controlled diet that reduced the risks of variation in feed availability and other sources of toxins. Veterinarians and other farm advisors should be aware of the potential for negative effects on animal health and production of fungal endophyte and the potential for Neotyphodium lolii to produce ergovaline.
Oxygen derived free radicals are normally generated in many metabolic pathways. These radicals may interact with various cellular components and induce cell injury. However, there is an efficient antioxidant system that protects the organism against free radical-induced cell injury. Oxidative stress results when there is a serious imbalance between generation of free radicals and the antioxidant capacity. When free radicals exceed the antioxidant capacity, cell injury causes diverse physiologic and pathologic changes. This paper reviews the mechanisms involved in the production, classification and effects that oxygen stress causes in the organism, as well as in the protective mechanism. Finally, analytical techniques and biochemical markers used to monitor oxidative stress are also described in this paper.
Summary The complex pattern of action for cell viability makes the heat shock protein (HSP) loci to potential candidate genes for stress susceptibility. In the bovine hsp70.1 gene a functional AP2 box variant affecting a significant decrease of cellular stress response, was described. To monitor the distribution of this promoter variant in phenotypically different populations a diagnostic PCR-RFLP assay was developed. As an indicator for individual stress susceptibility the phenotypic trait 'productive life' was measured based on the assumption that animals having longer 'productive life' might be superior in coping with stress during lifetime. Association of the observed promoter variant with the estimated breeding value 'productive life time' was studied in a Holstein sire population and a granddaughter design. Our observations suggest that this polymorphism affects productive life in cattle. Animals with a normal AP2 box are characterised by an increased stress tolerance concluded from their prolonged productive life. These results are supported by the observed different distribution of the hsp70.1 promoter variant in cows of different lactation numbers and degree of selection. Frequency of the mutant hsp70.1-AP2 box allele is significantly lower in cows selected as dams of sires and in cows with an increased lactation number. Additionally, cows with a mutant hsp70.1-AP2 box variant exhibited an increased hazard for culling.
Thermal stress can impact negatively on performance of intensively managed livestock in the southern United States and other subtropical and tropical regions of the world. Three funda- mental management practices, physical protection, genetic development and nutritional manage- ment schemes, have been proposed to alleviate partially the extent and severity of thermal stress. Focus of this paper is on i) interrelationships of thermal stress with functions involved in acqui- sition of nutrients and their metabolism, 2) considerations for provision of energy and nutrients during thermal stress and 3) potential practical management strategies to enhance animal pro- ductivity and efficiency. Discussion concentrates primarily on cattle. Acquisition of potentially absorbable nutrients and energy by the thermal-stressed animal is affected negatively by reduc- tion in dry matter intake, positively by slightly enhanced digestibility because of greater reten- tion time in the gut and, probably, negatively by reduced blood flow to and nutrient absorption from the alimentary tract. Negative influences of reduced intake and absorption of nutrients largely offset small enhancement in digestibility, resulting in less total nutrients being available to the thermal-stressed animal. Physiological adaptations to acute and(or) chronic thermal stress alter metabolism of absorbed energy substrates and nutrients. Hormones involved in adaptation to thermal stress include prolactin, growth hormone, thyroxine, glucocorticoids, antidiuretic hor- mone and aldosterone. These are either involved with nutrient partitioning and homeorhesis or with need for homeostatic regulation, potentiated by the thermal stressor. Increasing the energy density of diets fed to thermal-stressed animals by increasing concentrate to forage ratios or adding protected fat is discussed. For supplemental protein, the idea is suggested that increasing nutrient content may not always result in the most biologically and economically efficient production for a thermal-stressed animal. Water and macromineral needs, influenced heavily by demands to maintain homeostasis and homeothermy, are altered for lactating dairy cows. However, this may not be true for animals with lower turnover rates of these nutrients. A number of nutritional technologies are available to aid the thermal-stressed animal; others are not yet developed. Establishment of prediction equations for requirements of nutrients fed to livestock in different productive states during various intensities of thermal stress are needed. Forms of equations should describe the absolute nutrient needs (e.g., g.kg milk -1 -d -1 ) rather
Physiological state of dairy animals is a predisposing factor in environmental influences on animal health. Critical phases of life cycle include neonatal period, postpubertal reproduction, and lactation. Primary effect of environment in neonatal period is increased disease incidence associated with reduced immunoglobulin content in plasma of calves. Cold stress has little effect on reproduction; in contrast, heat stress reduces libido, fertility, and embryonic survival in cattle. Heat stress in late gestation reduces fetal growth and alters endocrine status of the dam. Carryover effects of heat stress during late gestation on postpartum lactation and reproduction also are detectable. Heat stress of lactating cattle results in dramatic reductions in roughage intake and rumination. Decreases in roughage intake contribute to decreased volatile fatty acid production and may contribute to alteration in ratio of acetate/propionate. Rumen pH also declines during thermal stress. Electrolyte concentrations, in particular sodium and potassium, also are reduced in rumen fluid of heat stressed cattle. The decrease in sodium and potassium are related to increases in loss of urinary sodium and loss of skin potassium as well as decline in plasma aldosterone and increase in plasma prolactin. Reduction in thyroxine, growth hormone, and glucocorticoid concentrations in chronically heat stressed cattle appear to be related to decreases in basal metabolism.
Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kg/d) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal NH4, and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumen-undegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%. Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear.
This paper examines whether or not responses of dairy cattle to various dietary macromineral elements differed in hot weather compared with thermoneutral conditions. The consequences of heat stress and the interrelationships of macromineral elements on feed intake, digestive function, use of dietary buffers, mineral element uptake from the portal-drained viscera, perturbation of acid-base physiology and related mineral element nutrition, effects of dietary macromineral element concentrations on lactational performance as affected by season, and influence of mineral elements in drinking water are reviewed, and new research results are presented. Dietary mineral buffers aided in alleviation of the decline in DMI and milk yield induced by heat stress. New research results showed that portal plasma flow declined with heat stress or by restriction of DMI in a thermoneutral environment and that uptake of P from the portal-drained viscera by lactating cows was reduced 50% by heat stress compared with that of cows with the same DMI in a thermoneutral environment. Accelerated respiration rate caused respiratory alkalosis and apparently compensated metabolic acidosis, changing the demand for Na and K during heat stress. There is need to characterize more accurately the nyctohemeral pattern of acid-base physiology in the heat-stressed lactating dairy cow and to relate it to macromineral element needs. A large data set (n = 1444 cow period means) was used to compare milk yield and DMI responses to varying dietary concentrations of P, Na, K, Cl, Ca, Mg, and cation-anion difference in summer compared with those in winter. Interactions of dietary concentrations of Cl, Ca, and Mg with season on DMI and K, Ca, and Mg with season on 4% FCM yield were detected. Interactions of Na by Cl, Na by P, and Cl by P with season on DMI and of Cl by P with season on 4% FCM yield were detected. High concentrations of sulfate and chloride in drinking water jeopardized productivity of cows during hot weather.
At 7 d postinoculation (DPI) with a mixed culture of avian Eimeria species, 21-d-old chicks maintained in batteries and floor
pens on a diet containing 0.15% (3 lb/ton) betaine plus 66 ppm (60 g/ton) salinomycin were significantly heavier and had significantly
lower feed conversion ratios and mortality than chicks fed diets containing 0.15% betaine or 66 ppm salinomycin alone, or
the control diet. At 31 DPI, when the chicks were 45 d old, the differences between the diet groups were not as great as at
7 DPI. In vitro, except at high concentrations, betaine was nontoxic to sporozoites of Eimeria tenella or Eimeria acervulina
and had little effect on their invasion and development in cultured cells. In vivo, invasion by E. tenella and E. acervulina
sporozoites was significantly reduced in all chicks fed diets containing betaine or salinomycin compared with that in control
chicks. There was a significant interaction between betaine and salinomycin that impacted on invasion by both species. Overall
development of E. tenella did not appear to be adversely affected by addition of betaine to diets containing salinomycin.
Conversely, development of E. acervulina was reduced in chicks fed diets containing 0.075% (1.5 lb/ton) betaine plus 66 ppm
salinomycin as compared with that in chicks fed salinomycin alone.
Liver abscesses in slaughtered beef cattle result from aggressive grain-feeding programs. The incidence, averaging from 12 to 32% in most feedlots, is influenced by a number of dietary and management factors. Liver abscesses represent a major economic liability to producers, packers, and ultimately consumers. Besides liver condemnation, economic impacts include reduced feed intake, reduced weight gain, decreased feed efficiency, and decreased carcass yield. Fusobacterium necrophorum, a member of the ruminal anaerobic bacterial flora, is the primary etiologic agent. Actinomyces pyogenes is the second most frequently isolated pathogen. Ruminal lesions resulting from acidosis generally are accepted as the predisposing factors for liver abscesses. F. necrophorum possesses or produces a number of virulence factors that participate in the penetration and colonization of the ruminal epithelium and subsequent entry and establishment of infection in the liver. However, only a few virulence factors have been characterized well. Control of liver abscesses in feedlot cattle generally has depended on the use of antimicrobial compounds. Five antibiotics (i.e., bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) are approved for prevention of liver abscesses in feedlot cattle. Tylosin is the most effective and the most commonly used feed additive. Tylosin feeding reduces abscess incidence by 40 to 70%. The mode of action of antibiotics in preventing liver abscesses is believed to be via inhibition of ruminal F. necrophorum. Protective immunity against F. necrophorum induced by a variety of antigenic components has ranged from ineffectual to significant protection.
Acute and chronic acidosis, conditions that follow ingestion of excessive amounts of readily fermented carbohydrate, are prominent production problems for ruminants fed diets rich in concentrate. Often occurring during adaptation to concentrate-rich diets in feedyards, chronic acidosis may continue during the feeding period. With acute acidosis, ruminal acidity and osmolality increase markedly as acids and glucose accumulate; these can damage the ruminal and intestinal wall, decrease blood pH, and cause dehydration that proves fatal. Laminitis, polioencephalomalacia, and liver abscesses often accompany acidosis. Even after animals recover from a bout of acidosis, nutrient absorption may be retarded. With chronic acidosis, feed intake typically is reduced but variable, and performance is depressed, probably due to hypertonicity of digesta. Acidosis control measures include feed additives that inhibit microbial strains that produce lactate, that stimulate activity of lactate-using bacteria or starch-engulfing ruminal protozoa, and that reduce meal size. Inoculation with microbial strains capable of preventing glucose or lactate accumulation or metabolizing lactate at a low pH should help prevent acidosis. Feeding higher amounts of dietary roughage, processing grains less thoroughly, and limiting the quantity of feed should reduce the incidence of acidosis, but these practices often depress performance and economic efficiency. Continued research concerning grain processing, dietary cation-anion balance, narrow-spectrum antibiotics, glucose or lactate utilizing microbes, and feeding management (limit or program feeding) should yield new methods for reducing the incidence of acute and chronic acidosis.
To determine whether nitric oxide (NO) production is increased in heat stroke (HS) patients.
A prospective analysis of nitrite and nitrate (NO2*/NO3) levels in ten HS patients was performed at the HS center in Makkah, Saudi Arabia.
Plasma (NO2*/NO3) levels were determined spectrophotometrically before cooling (0 time), and at 6, 12, and 24 h post-cooling.
The mean level of NO in the ten HS victims before cooling was significantly higher than in eight control patients (35.6+/-37.0 vs. 3.0+/-4.2 micromol/l; p<0.01). The levels were higher in non-survivors than in survivors. NO also correlated positively with the Acute Physiology and Chronic Health Evaluation II score (r = 0.72, p<0.018). There was no correlation between the NO level before cooling and blood pressure, rectal temperature, or cooling time.
HS is associated with excessive NO production, the magnitude of which is proportional to the severity of illness. NO may be an important mediator and integral part of the pathophysiological processes resulting in HS and may be a central factor linking the neurological and cardiovascular abnormalities observed in HS.
Enhanced expression of heat shock protein (HSP) has been shown to be protective against laboratory models of septic shock. Induction of HSPs to improve outcome in human disease has not been exploited because laboratory induction agents are themselves toxic and not clinically relevant. In this study, we demonstrate that a single dose of intravenous glutamine causes a rapid and significant increase in HSP25 and HSP72 expression in multiple organs of the unstressed Sprague-Dawley rat. With the utilization of a fluid-resuscitated rat model of endotoxemia, mortality was dramatically reduced by glutamine administration concomitant with the endotoxin injury. Endotoxin-treated animals given glutamine exhibited dramatic increases in tissue HSP expression and marked reduction of end-organ damage. These data suggest glutamine may protect against mortality and attenuate end-organ injury in endotoxemic shock via enhanced HSP expression. Furthermore, glutamine confers protection when administered at the initiation of sepsis, rather than as pretreatment. Thus glutamine appears to be a clinically viable enhancer of HSP expression and may prove beneficial in the therapy of sepsis and sepsis-induced organ injury.
Salt and heat stresses, which are often combined in nature, induce complementing defense mechanisms. Organisms adapt to high external salinity by accumulating small organic compounds known as osmolytes, which equilibrate cellular osmotic pressure. Osmolytes can also act as "chemical chaperones" by increasing the stability of native proteins and assisting refolding of unfolded polypeptides. Adaptation to heat stress depends on the expression of heat-shock proteins, many of which are molecular chaperones, that prevent protein aggregation, disassemble protein aggregates, and assist protein refolding. We show here that Escherichia coli cells preadapted to high salinity contain increased levels of glycine betaine that prevent protein aggregation under thermal stress. After heat shock, the aggregated proteins, which escaped protection, were disaggregated in salt-adapted cells as efficiently as in low salt. Here we address the effects of four common osmolytes on chaperone activity in vitro. Systematic dose responses of glycine betaine, glycerol, proline, and trehalose revealed a regulatory effect on the folding activities of individual and combinations of chaperones GroEL, DnaK, and ClpB. With the exception of trehalose, low physiological concentrations of proline, glycerol, and especially glycine betaine activated the molecular chaperones, likely by assisting local folding in chaperone-bound polypeptides and stabilizing the native end product of the reaction. High osmolyte concentrations, especially trehalose, strongly inhibited DnaK-dependent chaperone networks, such as DnaK+GroEL and DnaK+ClpB, likely because high viscosity affects dynamic interactions between chaperones and folding substrates and stabilizes protein aggregates. Thus, during combined salt and heat stresses, cells can specifically control protein stability and chaperone-mediated disaggregation and refolding by modulating the intracellular levels of different osmolytes.
Control of body temperature is a consequence of the thermoregulatory mechanism of an animal and the resistances to energy exchanges between it and the environment. To demonstrate the effects of thermoregulation and resistances on body temperature in beef cattle, some of the rele- vant research on genotypes of Bos indicus and Bos taurus has been reviewed: in particular, resist- ance of the tissues to transfer of metabolic heat to the skin which is lower in Bos indicus than in Bos taurus; resistance of the coat to solar radiation, which is greater for cattle with coat types similar to Bos indieus; the interaction of coat color and type in resisting environmental heat transfer to the skin; and some differences between Bos taurus and Bos indieus in the ability to increase and sustain evaporative heat-loss from the skin. Food and water availability also affect the control of body temperature in beef cattle. In Bos indicus, curtailing food intake significantly decreases the lower range of the daily body temperature cycle, whereas restricting water intake extends both maximum and minimum body temperatures. These alterations in temperature control promote energy and water conservation during dry seasons or drought; however~ they also are indicative of a physiological status that is not advantageous to production. The evidence is that a strictly regulated body temperature promotes the greatest productivity in beef cattle. Even small upward shifts in body temperature are deletrious to metabolic processes. As body temperature is a heritable trait, selection within breeds for thermoregulatory characteristics which defend this, such as efficient and sustained sweating rates and low resistances to heat-loss, would be a strategy for lifting productivity in the tropics. However, there is also genetic evidence from within a breed of Bos taurus cattle that changes toward increased capacity for thermoregulation are accompanied by a reduction in inherent energy metabolism. Nevertheless a greater proportion of possible produc- tion is realized in cattle with more strictly controlled body temperatures.
Rectal temperatures of cattle grazed near the tropic of Capricorn in central Queensland were studied. The cattle were of Bos indicus, B. taurus and crossbred lines, and were represented by over 200 growing heifers in each of 2 years and some supplementary groups.
Rectal temperatures were log e normally distributed when they were expressed as deviations from a basal temperature of 38°C. They were significantly repeatable, but were more highly repeatable when herd mean temperature was above 39·5°C. The heritability estimate was 0·33 ( P < 0·01).
The mean phenotypic regression of growth rate on rectal temperature, within breed groups, was 0·04 (s.e. 0·006) kg/day per °C ( r = 0·3, P < 0·01) over the entire growth period from birth to 18 months of age but greater during warmer seasons. The estimated genetic correlation was insignificant in one group of heifers but −0·86 (s.e. 0·17) in the other.
The evidence of favourable and possible unfavourable responses to selection of cattle for low rectal temperature in warm environments is discussed.
Proton and/or sodium electrochemical gradients are critical to energy handling at the plasma membranes of all living cells. Sodium gradients are used for animal plasma membranes, all other living organisms use proton gradients. These chemical and electrical gradients are either created by a cation pumping ATPase or are created by photons or redox, used to make ATP. It has been established that both hydrogen and sodium ions leak through lipid bilayers at approximately the same rate at the concentration they occur in living organisms. Although the gradients are achieved by pumping the cations out of the cell, the plasma membrane potential enhances the leakage rate of these cations into the cell because of the orientation of the potential. This review proposes that cells use certain lipids to inhibit cation leakage through the membrane bilayers. It assumes that Na+ leaks through the bilayer by a defect mechanism. For Na+ leakage in animal plasma membranes, the evidence suggests that cholesterol is a key inhibitor of Na+ leakage. Here I put forth a novel mechanism for proton leakage through lipid bilayers. The mechanism assumes water forms protonated and deprotonated clusters in the lipid bilayer. The model suggests how two features of lipid structures may inhibit H+ leakage. One feature is the fused ring structure of sterols, hopanoids and tetrahymenol which extrude water and therefore clusters from the bilayer. The second feature is lipid structures that crowd the center of the bilayer with hydrocarbon. This can be accomplished either by separating the two monolayers with hydrocarbons such as isoprenes or isopranes in the bilayer's cleavage plane or by branching the lipid chains in the center of the bilayers with hydrocarbon. The natural distribution of lipids that contain these features are examined. Data in the literature shows that plasma membranes exposed to extreme concentrations of cations are particularly rich in the lipids containing the predicted qualities. Prokaryote plasma membranes that reside in extreme acids (acidophiles) contain both hopanoids and iso/anteiso- terminal lipid branching. Plasma membranes that reside in extreme base (alkaliphiles) contain both squalene and iso/anteiso- lipids. The mole fraction of squalene in alkaliphile bilayers increases, as they are cultured at higher pH. In eukaryotes, cation leak inhibition is here attributed to sterols and certain isoprenes, dolichol for lysosomes and peroxysomes, ubiquinone for these in addition to mitochondrion, and plastoquinone for the chloroplast. Phytosterols differ from cholesterol because they contain methyl and ethyl branches on the side chain. The proposal provides a structure-function rationale for distinguishing the structures of the phytosterols as inhibitors of proton leaks from that of cholesterol which is proposed to inhibit leaks of Na+. The most extensively studied of sterols, cholesterol, occurs only in animal cells where there is a sodium gradient across the plasma membrane. In mammals, nearly 100 proteins participate in cholesterol's biosynthetic and degradation pathway, its regulatory mechanisms and cell-delivery system. Although a fat, cholesterol yields no energy on degradation. Experiments have shown that it reduces Na+ and K+ leakage through lipid bilayers to approximately one third of bilayers that lack the sterol. If sterols significantly inhibit cation leakage through the lipids of the plasma membrane, then the general role of all sterols is to save metabolic ATP energy, which is the penalty for cation leaks into the cytosol. The regulation of cholesterol's appearance in the plasma membrane and the evolution of sterols is discussed in light of this proposed role.
High ambient temperatures, high direct and indirect solar radiation, and humidity are environmental stressing factors that impose strain on animals. This review concerns the heat stress–strain response of domestic ruminants from the viewpoint of animal welfare. Despite having well developed mechanisms of thermoregulation, ruminants do not maintain strict homeothermy under heat stress. There is unequivocal evidence that hyperthermia is deleterious to any form of productivity, regardless of breed, and stage of adaptation. The best recognized effect of raised body temperature is an adaptive depression of the metabolic rate associated with reduced appetite. Thus, in domestic ruminants a rise of body temperature marks the transition from aversive stage to noxious stage. Physiological (sweating, panting), hormonal (cortisol, thyroid gland activity), and behavioral thermoregulatory responses are discussed in respect to animal welfare. Factors such as water deprivation, nutritional imbalance and nutritional deficiency may exacerbate the impact of heat stress. The higher sensitivity of cattle to heat stress in comparison with sheep, and of animals at various productive stages in comparison with animals at maintenance is highlighted. Some practical measures that are applicable under extensive conditions, such as provision of shade shelter, are suggested.
SUMMARY The physiological effects of lactic acidosis in feedlot cattle may range from temporary in- appetence to acute physiological alterations terminating in death. Physiopathology resulting from ruminal accumulation and subsequent absorption of lactic acid include rumen stasis, diarrhea and dehydration, systemic acidosis and, in acute forms of lactic acidosis, cardio- vascular and respiratory failure. The rate of lactic acid absorption per unit time and not the total quantity absorbed appears to determine whether compensatory mechanisms remain functional and maintain the hydrogen ion concentration of body fluids within a compati- ble range.
A total of 252 untrained, unacclimatized, and unanesthetized laboratory rats weighing between 485 and 545 g were fasted and either run to exhaustion at 5, 20, 23, or 26 degrees C or were restrained and heated at an ambient temperature of 41.5 degrees C. The incidence of mortality associated with a wide range of work-induced hyperthermias was compared to the lethality of equivalent heat loads in the absence of physical effort. The severity of hyperthermia was calculated in degree-minutes above a base-line core temperature of 40.4 degrees C. The LD25's of run-exhausted versus restrained-heated rats were 16.8 and 30.1 deg-min, respectively. Survivors had a faster cooling rate than fatalities, but run-exhausted survivors had a slower cooling rate than restrained-heating survivors. Results indicate that 1) both the incidence of mortality and the survival time can be predicted from the severity of core heating, 2) work-related factors contribute to an increased rate of heatstroke death at low thermal loads, and 3) retrospectively, both heat-sensitive and heat-resistant groups were identified.
This study was undertaken to develop an anesthetized dog heatstroke model. Forty-six animals were anesthetized with pentobarbital sodium (25 mg/kg) intravenously, and maintained at an ambient temperature of (42-46 degrees C) with a water-heated blanket over 2.5-3.0 h until rectal temperatures rose to 43.0-44.5 degrees C. Animals then cooled passively until death occurred or until 18 h elapsed, and were prepared for autopsy. Liver, kidney, and brain temperature, mean weighted skin temperature, mean weighted surface heat loss, and metabolic rates were obtained. There were no significant differences between liver, kidney, brain, and rectal temperatures during the heating and cooling periods. Cardiac output rose to 127% of initial value, and dropped rapidly to zero at 43.4 degrees C rectal temperature. The rapid decline was accompanied by a doubling of heart rate and a rapid drop in blood pressure and respiratory rate. Cheyne-Stokes respiration and apnea preceded bradycardia followed by asystole or ventricular fibrillation. Certain serum constituents demonstrated modest elevations suggestive of widespread tissue damage. Autopsy did not reveal a clear pattern of heat injury, with the exception of consistent congestion of the major organs and karyorrhexis of lymphocytes. These data are in agreement with similar data from human heatstroke victims and other heatstroke modeling in dogs, and support the concept that the anesthetized dog can in many respects provide an adequate model for human heatstroke.
SUMMARY Acidosis in cattle is caused by excessive ingestion of feeds which are rich in readily available carbohydrates. Thus, factors which contribute to excessive ingestion of high energy diets are predisposing to acidosis. Many of the conditions which prevail in cattle feedlots contribute to variable feed intake by cattle and subsequently to acidosis. A multitude of management factors are involved in successfully feeding large numbers of cattle under typical feedlot conditions. Management is most critical during the follow- ing periods: 1) starting cattle on feed, 2) graduating cattle to higher concentrate rations, 3) during changes in weather, 4) during long periods on a finishing diet, and 5) when cattle are extremely hungry due to feeding problems or errors. There appear to he some breed differences in
Lipopolysaccharide increases intestinal mucosal permeability to hydrophilic compounds such as chromium 51-labeled edetate (51Cr-EDTA). We sought to determine whether this phenomenon is partly mediated by lipopolysaccharide-induced mesenteric hypoperfusion. We assessed permeability in an isolated segment of ileum by measuring plasma-to-lumen clearances (C) for two probes, 51Cr-EDTA and urea, and expressing the results as a ratio (CEDTA/CUREA). In control pigs (n = 6) resuscitated with Ringer's lactate (RL), mucosal permeability was unchanged during the 210-minute period of observation. In pigs (n = 7) infused with lipopolysaccharide (50 micrograms/kg) and similarly resuscitated with RL, mesenteric perfusion (Qsma) decreased significantly and permeability increased progressively and significantly. When endotoxic pigs (n = 6) were resuscitated with a regimen (RL plus hetastarch plus dobutamine) that preserved normal Qsma, lipopolysaccharide-induced mucosal hyperpermeability was prevented. Resuscitation of endotoxic pigs (n = 6) with RL plus hetastarch provided intermediate protection against both mesenteric hypoperfusion and increased permeability. These data suggest that diminished Qsma contributes to impaired ileal mucosal barrier function in experimental endotoxicosis.
To find out a critical point of physiological responses of steers which would finally lead to death due to heat stress, four Holstein steers weighing about 300 kg were housed in an artificial climatic room and exposed to each of the following room temperature and relative humidity: 35 degrees C and 70 per cent, 36 degrees C and 80 per cent, 38 degrees C and 70 per cent, and 42 degrees C and 60 per cent. Sequential clinical and hematological examinations were carried out during thermal loads on the steers, and pathological examinations after their death or slaughter. All the steers manifested panting, rise of rectal temperature, reduction or disappearance of peristalsis, hypersalivation, dysfunction of the skin reflex, and remarkable decrease in white blood cell count and pressure of CO2 (Pco2) value of jugular blood. At the end of heat stress, an animal would be survived if it meet the following conditions: (1) rectal temperature was below 42.7 degrees C, (2) the respiration rate did not decrease to one half (about 100/minute) of the maximum rate during the exposure period, (3) peristalsis and skin reflex disappeared almost completely, (4) the white blood cell count did not decrease to less than 50 per cent of the normal level, and (5) the Pco2 value of venous blood was maintained at a level of more than 15 mmHg. Cloudy discoloration with a boiled-meat appearance was noticed in the skeletal muscle of the hind part of the body in two dead cases. No significant changes were detected in any other steer slaughtered several days after release from the thermal stress.
Elevated temperature rapidly increases expression of genes for heat shock proteins (HSP), including HSP-70. The response is presumably triggered by denaturation of cell proteins and helps in their renaturation. Hypertonicity may also denature proteins, but the protective response, which is accumulation of compatible organic osmolytes [including betaine and inositol in Madin-Darby canine kidney (MDCK) cells], apparently differs and is slow. Recently, hypertonicity was found also to increase expression of HSP-70 in MDCK cells, a response proposed to provide protection until organic osmolytes can accumulate. Our purpose was to examine whether 1) a gene involved in accumulation of organic osmolytes also responds to heat stress and 2) whether accumulation of organic osmolytes affects expression of HSP-70. We find that 1) the betaine transporter mRNA, which is greatly increased by hypertonicity (515 vs. 315 mosmol), is unaffected by high temperature (42 degrees C vs. 37 degrees C); 2) hypertonicity-induced increases in HSP-70 and betaine transporter mRNA are much greater when the medium (and cell) contain no betaine and no inositol than when high concentrations of these are present; and 3) high betaine greatly inhibits the increase in HSP-70 mRNA at high temperature. We conclude the following. 1) Although heat shock and betaine transporter genes both respond to hypertonicity, the betaine transporter is not a HSP. 2) Accumulation of organic osmolytes attenuates the HSP-70 response to hypertonicity, as it might if the HSP-70 expression were a temporizing response. 3) Betaine inhibits HSP-70 response to elevated temperature, presumably by its known effect of stabilizing proteins.
Recently, investigators have reported that heat shock proteins (HSPs) can protect isolated cells from cytotoxicity induced by two important mediators of sepsis: interleukin-1 and tumor necrosis factor. The present study was undertaken to examine the hypothesis that transient whole body hyperthermia could decrease mortality from subsequent challenge with gram-negative endotoxin. We demonstrate that heat pretreatments improved long-term survival fivefold in a mouse endotoxin model and this was correlated with the production of HSPs. There was a marked difference in individual organ expression of the inducible 72-kDa heat shock protein (HSP72). Heat treatments caused significant HSP72 formation in lung, liver, kidney, and small intestine, but much lesser formation in heart, brain, and abdominal wall muscle. Additional experiments demonstrated that the protective effect of hyperthermic treatments against an endotoxin challenge occurred early, i.e., 1 and 2 h after heating, was maximal at 12 h, and had significantly diminished by 48 h. The formation and decay of HSP72 demonstrated a time course that paralleled the survival curve from endotoxin challenge, thus suggesting a possible role for HSP72 in the protective effect. Surprisingly, and in contrast to studies reported in incubated cells, endotoxin alone did not cause significant formation of HSP72 in vivo.
Induced expression of the HSP70 gene in 3T3 and SV-3T3 cells was monitored by measurements of the synthesis of HSP70 and of the cellular contents of both HSP70 and its mRNA. The presence of betaine (N-trimethylglycine) at concentrations of 2.5-25 mM decreased the induction of HSP70 gene expression caused by incubation of 3T3 and SV-3T3 cells in hypertonic (0.5 osM) medium. This effect was accompanied by an enhancement of SV-3T3 cell adaptation, assayed by colony formation, to the hyperosmotic conditions. In contrast, the presence of betaine did not affect HSP70 gene expression induced in these cells by heat shock. After 6 h incubation with 25 mM betaine under hypertonic (0.5 osM) conditions the intracellular concentration of betaine in SV-3T3 cells was about 195 mM, compared with about 70 mM under isotonic (0.3 osM) conditions. Hence, with this concentration of extracellular betaine, the marked increase in the accumulation of betaine within the cells presumably counteracts the imposed osmotic pressure and eliminates the signal that otherwise initiates increased expression of the HSP70 gene.
Classical heat stroke is a rare disease in moderate climates. We report a patient who demonstrated the classical triad of elevated body temperature, neurological disturbances, and anhidrosis. He developed rhabdomyolysis and acute renal failure. Eventually he died. Since manifestations of classical heat stroke appear to mimic an acute phase response, cytokines are thought to play an important role in its pathogenesis.
Recent reports show that a pre-heat shock has a protective effect against endotoxin "in vivo" in rodents. It has remains unclear what actually confers the protection against endotoxin. One candidate for this protective effect is the heat shock protein of 70 kDa (HSP70). We found that a mild heat shock pretreatment is the rat myogenic cell line, H9c2(2-1), confers resistance to a subsequent exposure to endotoxin. A myogenic rat cell line stably transfected with the human inducible HSP70 exhibits an increased survival rate compared with cells stably transfected solely with the selectable neomycin marker gene or the parental cell line H9c2(2-1) when exposed to endotoxin. The mechanism of endotoxin-induced cell injury is postulated to be through the generation of nitric oxide in these myogenic cells during exposure to endotoxin. We conclude that HSP70, regardless of the particular mechanism of cytotoxicity, plays a role in protecting the cell against the deleterious effects of endotoxin.
Medium osmolarity sensitively regulates Kupffer cell functions like phagocytosis and prostaglandin (PG) and cytokine production. Betaine and taurine, recently identified as osmolytes in liver cells, interfere with these effects. Because Kupffer cell activation is an important pathogenic mechanism in ischemia-reoxygenation injury, the influence of osmolarity and osmolytes was investigated in a rat liver perfusion model of warm ischemia. Livers were perfused with different medium osmolarities for 60 to 90 minutes in the absence of oxygen, followed by another 90 minutes of reoxygenation. Lactate dehydrogenase (LDH) leakage into the effluent perfusate during the hypoxic and the reoxygenation period was eight- to 10-fold higher with a medium osmolarity of 385 mosmol/L than in normo-osmolarity, and further decreased with hypo-osmolar perfusion buffer. Betaine and taurine addition to the perfusate in near physiological concentrations decreased hypoxia-reoxygenation-induced LDH leakage, aspartate transaminase (AST) leakage, and perfusion pressure increase in hyperosmolar and normo-osmolar perfusions. Stimulation of PGD2, PGE2, thromboxane B2 (TXB2), and tumor necrosis factor alpha (TNF-alpha) release, as well as induction of carbon uptake by the liver during reoxygenation, were suppressed by betaine and taurine, pointing to an interference of these osmolytes with Kupffer cell function. In contrast, endothelial cell function as assessed by hyaluronic acid (HA) uptake was not influenced. It is concluded that warm ischemia-reoxygenation injury in rat liver is aggravated by hyperosmolarity and attenuated by hypo-osmolarity. The osmolytes betaine and taurine have a protective effect, presumably by inhibition of Kupffer cell activation.
To further elucidate mechanisms underlying the higher heat tolerance of physically fit compared with sedentary people, we have investigated the possibility that endotoxins (of gastrointestinal origin) act, as in the normal development of fever, to raise body temperature and therefore reduce heat tolerance. In an initial series of experiments, five physically fit and four sedentary sheep were exposed twice at rest to an environment of 42/35 degrees C (dry/wet bulb temperature). When animals were given normal saline i.v., rectal temperature (Tre) rose at a significantly higher rate in sedentary than in fit animals; this confirms that heat tolerance is improved by physical fitness. Treatment with i.v. indomethacin did not affect the rate of rise of Tre in fit animals. In sedentary animals, however, Tre was lowered to approximate that of fit animals. Because indomethacin blocks prostaglandin pathways involved in endotoxin-induced fever, the indomethacin-induced improvement of heat tolerance of sedentary but not fit animals supports the contention that endotoxins play a role in determining that difference in heat tolerance. In a second series of experiments, quantitative cardiovascular measurements were made by using radioactive microspheres. Under normothermic conditions, blood flows in the brain, ileum, and diaphragm were higher in fit than in sedentary animals. During hyperthermia up to Tre of 42 degrees C (in a 42/39 degrees C environment), fit compared with sedentary animals exhibited 1) a greater increase in cardiac output, 2) an increase in blood flow through arteriovenous anastomoses to higher and better maintained levels, 3) less reduction in blood flow to the ileum, and 4) greater increase in blood flows to the myocardium, turbinates, nasal mucosa, and respiratory muscles. Endotoxins are likely to come from the gut lumen, because reduction of gut blood flow forms part of the normal response to heat stress. We suggest that improvement of heat tolerance by physical fitness is caused by a greater cardiovascular capacity that permits not only greater perfusion of heat-loss tissues but the maintenance of a better gastrointestinal tract blood supply, thereby better maintaining the normal barrier to movement of endotoxins from gut lumen to plasma. Sedentary people, with their lower cardiovascular capacity, redistribute more blood flow away from the gut during environmentally induced hyperthermia, thus allowing endotoxin-induced fever to aggravate hyperthermia.
Morbidity and mortality of feedlot cattle have a variety of causes. Compared to respiratory disease, metabolic and digestive disorders generally are less prevalent and occur later in the feeding period. In addition to the obvious costs related to animal death and medication, subsequent performance of sick cattle often is depressed substantially. Closer coordination between veterinarians, nutritionists, and feedlot managers should help reduce the incidence of morbidity and mortality of feedlot cattle.
The effect of betaine and salinomycin on absorption of methionine and glucose in tissue from the duodenal loops of Eimeria acervulina-infected chicks was determined. Differences in the ultrastructure of the intestinal cells and parasite developmental stages were also examined. With a drug-resistant isolate of E. acervulina, methionine absorption was significantly higher in chicks fed a basal diet supplemented with 0.15% betaine as compared with absorption in chicks fed the unsupplemented basal diet. Addition of 66 ppm salinomycin to the diet containing betaine did not further enhance absorption. Conversely, with a drug-sensitive isolate, methionine absorption was significantly higher in chicks fed a diet supplemented with both betaine and salinomycin than in chicks fed the unsupplemented basal diet. Tissue from chicks fed any of the supplemented diets was usually significantly heavier than that from chicks fed the unsupplemented diet, even when weight gains of the birds were similar. Glucose absorption was similar in all diet groups. Epithelial cells in coccidia-infected and uninfected chicks fed diets supplemented with betaine or betaine plus salinomycin were less electron dense than cells from chicks fed diets that were not supplemented with betaine. Merozoites of E. acervulina in chicks fed diets supplemented with salinomycin had extensive membrane disruption and vacuolization, but the damage was prevented when betaine was added to the diet. Numerous merozoites and intact schizonts were seen in the intestinal lumen of chicks fed the diet containing betaine plus salinomycin.
Exposure of conscious animals to environmental heat stress increases portal venous radical content. The nature of the observed heat stress-inducible radical molecules suggests that hyperthermia produces cellular hypoxic stress in liver and intestine. To investigate this hypothesis, conscious rats bearing in-dwelling portal venous and femoral artery catheters were exposed to normothermic or hyperthermic conditions. Blood gas levels were monitored during heat stress and for 24 h following heat exposure. Hyperthermia significantly increased arterial O2 saturation, splanchnic arterial-venous O2 difference, and venous PCO2, while decreasing venous O2 saturation and venous pH. One hour after heat exposure, liver glycogen levels were decreased approximately 20%. Two hours after heat exposure, the splanchnic arterial-venous O2 difference remained elevated in heat-stressed animals despite normal Tc. A second group of rats was exposed to similar conditions while receiving intra-arterial injections of the hypoxic cell marker [3H]misonidazole. Liver and intestine were biopsied, and [3H]misonidazole content was quantified. Heat stress increased tissue [3H]misonidazole retention 80% in the liver and 29% in the small intestine. Cellular [3H]misonidazole levels were significantly elevated in intestinal epithelial cells and liver zone 2 and 3 hepatocytes and Kupffer cells. This effect was most prominent in the proximal small intestine and small liver lobi. These data provide evidence that hyperthermia produces cellular hypoxia and metabolic stress in splanchnic tissues and suggest that cellular metabolic stress may contribute to radical generation during heat stress.
The objectives were to characterize biochemical changes, focusing on the antioxidant defense system, in stratified squamous and oxyntic mucosae in pigs fed diets with differing propensity to promote gastric lesions. Barrows (n = 24; 48.7+/-1.0 kg BW) housed in individual pens were used in the experiment. Barrows were fed a corn-soybean meal diet. Half of the animals were fed the diet as a coarsely ground meal (CGM; average particle size = 886 microm), and half were fed the diet as a finely ground pelleted (FGP; average particle size = 528 microm) feed. Initiation and termination of the experiment were staggered over a 3-wk period. Diets were fed for 6 wk. Visual evaluation of the stratified squamous mucosa of the proximal stomach showed increased (P<.001) damage in animals fed the FGP diet. These results were supported by histological evaluation. Thiobarbituric acid-reacting substances (TBARS), indicative of peroxide generation, relative to amount of protein were higher (P<.001) in stratified squamous than in oxyntic mucosa, and, per unit of tissue, TBARS were highest in stratified squamous mucosa of animals fed the FGP diet. Glutathione peroxidase activity followed a pattern similar to that of peroxides. Prostaglandin E2 was higher (P<.004) in stratified squamous than in oxyntic mucosa. In contrast, the activity of catalase was higher (P<.001) in oxyntic mucosa and was not affected by diet. The data show differences in the production of peroxides, the antioxidant defense system, and PGE2 between stratified squamous and oxyntic mucosae. Generation of prooxidants and the antioxidant defense system may play a role in the predilection of ulcers for the stratified squamous mucosal region of the pig stomach.
Two experiments were conducted to evaluate the impact of housing density on the stomach morphology of growing pigs and determine whether there was an interaction between housing density and diet. All diets were corn-soybean meal based. In Exp. 1, 42 barrows (41.0+/-.95 kg BW) were allotted either individually or three pigs per pen to evaluate the effects of crowding on stomach lesions. Pen space per pig was 1.54 and .51 m2, respectively. All pigs were fed a finely ground and pelleted diet (610 microm) for 6 wk. The ADG decreased (P<.05) for the pigs housed three per pen during wk 4 to 6 only. There was no effect of housing density on feed intake or gain/feed ratio. Neither visual nor histological ulcer score differed between the two treatment groups. No stomachs were graded as normal. In Exp. 2, 80 barrows (39.8+/-.9 kg BW) were allotted either two or four pigs per pen. Pen space per pig was .77 and .39 m2, respectively. Half of the pigs in each housing situation were fed a coarse meal diet (1,050 microm), and half of the pigs were fed a finely ground and pelleted diet (577 microm) throughout the 49-d experimental period. Throughout the trial, pigs housed two per pen gained at a greater rate (P<.05) than pigs housed four per pen. From d 14 to the end of the trial, pigs consuming the finely ground and pelleted diet gained at a greater rate (P<.05) than pigs fed the coarse meal diet. The differences in ADG were reflected in final body weight. Stomach weight as a percentage of body weight was higher for animals on the coarse meal diet. Visual and histological ulcer scores were similar, and both were higher (P<.001) on the finely ground and pelleted diet, indicating greater damage. There was no effect of space restriction on stomach morphology. These data show the major effect of diet type on stomach lesions with no interaction with space restriction.
This work tested the hypotheses that splanchnic oxidant generation is important in determining heat tolerance and that inappropriate.NO production may be involved in circulatory dysfunction with heat stroke. We monitored colonic temperature (T(c)), heart rate, mean arterial pressure, and splanchnic blood flow (SBF) in anesthetized rats exposed to 40 degrees C ambient temperature. Heating rate, heating time, and thermal load determined heat tolerance. Portal blood was regularly collected for determination of radical and endotoxin content. Elevating T(c) from 37 to 41.5 degrees C reduced SBF by 40% and stimulated production of the radicals ceruloplasmin, semiquinone, and penta-coordinate iron(II) nitrosyl-heme (heme-.NO). Portal endotoxin concentration rose from 28 to 59 pg/ml (P < 0.05). Compared with heat stress alone, heat plus treatment with the nitric oxide synthase (NOS) antagonist N(omega)-nitro-L-arginine methyl ester (L-NAME) dose dependently depressed heme-.NO production and increased ceruloplasmin and semiquinone levels. L-NAME also significantly reduced lowered SBF, increased portal endotoxin concentration, and reduced heat tolerance (P < 0.05). The NOS II and diamine oxidase antagonist aminoguanidine, the superoxide anion scavenger superoxide dismutase, and the xanthine oxidase antagonist allopurinol slowed the rates of heme-.NO production, decreased ceruloplasmin and semiquinone levels, and preserved SBF. However, only aminoguanidine and allopurinol improved heat tolerance, and only allpourinol eliminated the rise in portal endotoxin content. We conclude that hyperthermia stimulates xanthine oxidase production of reactive oxygen species that activate metals and limit heat tolerance by promoting circulatory and intestinal barrier dysfunction. In addition, intact NOS activity is required for normal stress tolerance, whereas overproduction of.NO may contribute to the nonprogrammed splanchnic dilation that precedes vascular collapse with heat stroke.
An early event in endotoxin-induced tissue injury is adhesion and migration of leukocytes through the endothelium. This is a three-stage process, initially low-grade selectin-mediated adhesion, seen as a decrease in rolling velocity, followed by integrin-mediated adhesion and transmigration. Thermotolerance has been shown to reduce tissue injury and mortality induced by endotoxin. The aim of this study was to investigate the effect of thermotolerance on leukocyte-endothelial interactions. Intravital video microscopy was used to examine hemodynamic parameters, leukocyte rolling, adhesion, and migration in rat mesenteric postcapillary venules. Sprague-Dawley rats were randomized into control, lipopolysaccharide (LPS), and thermotolerance + LPS groups. Thermotolerance was induced 18 h prior to administration of LPS by elevating core body temperature to 41 + 0.5 degrees C for 15 min. LPS (055:B5 15 mg/kg) was administered via the jugular vein after baseline recording. Leukocyte rolling velocity and the number of adherent and migrated leukocytes were measured by intravital microscopy at baseline 0 min and 10, 30, 60, and 90 min after LPS administration. Heat shock protein 72 (HSP72) expression in tissues was determined by Western immunoblotting. The results indicated that LPS administration significantly decreased leukocyte rolling velocity during endotoxemia and increased leukocyte adhesion (10.3 +/- 1.67, 13.2 +/- 1.40, and 10.0 +/- 1.57/100 microm) and migration (5.7 +/- 1.02 and 8.3 +/- 1.76/field) at 30, 60, and 90 min after LPS injection (P < 0.01 vs baseline and control group). Thermotolerance maintained leukocyte rolling velocity and significantly reduced leukocyte adhesion (5.7 +/- 0.88 and 4.0 +/- 0.68/100 microm) and migration (2.8 +/- 0.32 and 3.0 +/- 0.68/field) at 30 and 60 min after LPS administration (P < 0.01 and 0.05 vs LPS group). Expression of HSP72 was induced in mesentery, gut, and lung by thermotolerance. This study indicates that thermotolerance attenuated LPS-induced microvascular injury by decreasing leukocyte-endothelial adhesion and migration.
The efficiency of betaine absorption into small intestinal slices of broiler chicks was studied in vitro with 14C-labeled betaine. The relative proportion of Na+-coupled betaine uptake, as well as the total uptake capacity was larger in the duodenum than in the jejunum. Dietary betaine increased the Na+-coupled uptake in the duodenum. In in vivo-experiments, methyl-14C-labeled betaine, methionine, or choline was fed to broiler chicks. Betaine appeared in the blood more rapidly, and reached a higher total concentration than choline or methionine. The data suggest that choline and methionine were associated with plasma lipoproteins whereas betaine remained free in the plasma. The label distribution in liver, kidney, and intestinal tissues was studied 24 h after label ingestion. Most of the label from betaine was found in the aquaeous phase in the muscle, while in the liver and jejunum the label from betaine was distributed more evenly between the aquaeous, lipid, and protein phases. Label from choline accumulated in the lipid fraction, particularly so in the liver, whereas label from methionine showed a more variable distribution pattern. The distribution results are interpreted in terms of specific roles of betaine, choline, and methionine in methyl group metabolism.
In Experiment 1, the water holding capacity of broiler chick intestinal tissue was studied in vitro. The chicks were fed with corn-based diets with or without a 0.2% betaine supplementation in the drinking water. Slices from duodenum and jejunum were incubated in iso-osmotic (300 mM) or hyperosmotic saline (600 mM) with or without 10 mM betaine. The water volume of tissue slices was studied by adding tritiated water in the incubation medium while [14C]inulin was used to correct for the adherent water. After 30 min of incubation, by which time the steady-state of tritium influx had been achieved, the 3H and 14C-activities of the tissue slices were measured. The ileal and duodenal tissues incubated in the hyperosmotic saline accumulated less tritium than those incubated in iso-osmotic saline. Duodenal slices incubated in hyperosmotic saline with the presence of betaine showed a tritium content similar to slices incubated in iso-osmotic saline. The data suggest that the presence of betaine helped the duodenal, but not jejunal, epithelium to maintain water balance in hyperosmotic conditions. The dietary betaine supplementation diminished the differences between the incubation treatments in duodenal, but not in ileal tissue. In Experiment 2, the same double labeling method, but with shorter incubation times, was used to assess the rate of water flux from the incubation medium to duodenal or jejunal slices. The dietary treatments (as in Experiment 1) had little effect on the results. Betaine in the hyperosmotic saline significantly decreased the rate of tritium accumulation into the tissue slices, indicating that betaine slowed down the influx of water to the epithelium. We suggest that betaine affects the movement of water across the intestinal epithelium and has a role in the osmoregulation of small intestine of broiler chicks.
Pathologic data from the gastrointestinal tract in heat-stroke victims, although documented, are confusing. The object of this study was to document the gastrointestinal changes observed during induced total body hyperthermia (42 degrees C) followed by cooling. An established heat-stroke model was used in a university animal laboratory. Group A underwent immersion hyperthermia for 1 hour, followed by cooling to normothermia. Group B underwent hyperthermia to cardiac arrest, followed by resuscitation plus cooling to normothermia. The postmortem findings in the gastrointestinal tract were evaluated. In group A, several hours after return to normothermia and stable vital signs, delayed secondary deterioration with massive gastrointestinal bleeding occurred. The postmortem findings revealed bleeding into the whole intestine and serosanguineous fluid in the peritoneal cavity. In group B, an adynamic gut was observed after 165 +/- 21 minutes (range 125-174) of heating when mean arterial pressure (MAP) decreased to 38 +/- 21 mm Hg (range 30-70). Cardiac arrest occurred at 178 +/- 26 minutes (range 140-208) of immersion. Eight monkeys could be resuscitated to spontaneous circulation with return of normal gut motility, then they rearrested at 158 +/- 68 minutes (range 45-228). The postmortem findings resembled those in group A. The Postmortem findings in the four monkeys in which restoration of spontaneous circulation failed, revealed only some intestinal wall edema and occasional petechial hemorrhages. It is concluded that after a hyperthermic event, tissue injury continues to develop. The pathologic findings are related to the time lapse between hyperthermia, cooling, and death. The similarity to the descriptions of septic shock, multiple organ failure, and the gut reperfusion syndrome is striking. An immunologic response as a mechanism for all these syndromes is discussed.
The aim of this experiment was to study the patterns of betaine accumulation into intestinal tissue, liver and plasma of broiler chicks with or without coccidial infection. The chicks were raised on a corn-based, low-betaine diet with or without 1000 ppm betaine supplementation and with or without intestinal microparasite (Eimeria maxima) challenge to the age of 21 days. Plasma, liver, intestinal tissue and digesta of non-challenged (NC) birds and plasma and intestinal tissue of coccidiosis challenged (CC) birds were analysed for betaine content. NC birds were also analyzed for homocysteine in plasma and S-adenosylmethionine (S-AM) in liver. The jejunal epithelium was histologically examined for the presence of coccidia and the crypt-villus ratio was measured. Dietary betaine supplementation decreased the plasma homocysteine concentration but had no effect on liver S-AM of NC birds. The data suggest that chicks on a low-betaine diet accumulate betaine into the intestinal tissue. When the diet was supplemented with betaine, betaine accumulated heavily into liver and to a lesser degree into intestinal tissue. The concentration of betaine in jejunal and ileal digesta was low suggesting that dietary betaine was mainly absorbed from the proximal small intestine. The coccidial challenge decreased the concentration of betaine in the liver, but greatly increased that in the intestinal tissue. The crypt-villus ratio was decreased by the dietary betaine supplementation in healthy and challenged chicks, suggesting that dietary betaine both protects the jejunal villi against coccidial infection and also stabilizes the mucosal structure in healthy broiler chicks. These results support our earlier findings suggesting that betaine is likely to act as an important intestinal osmolyte in broiler chicks.
The most basic mechanism of cellular protection involves the expression of a highly conserved family of essential proteins, known as heat shock or stress proteins (HSPs). The expression of these proteins after a sublethal insult can induce "stress tolerance" and protect against a subsequent stress that otherwise would be lethal. Experimental data have shown that preinduction of the heat stress response can provide marked protection against many forms of cellular injury, including ischemia and reperfusion, lung injury, and shock. However, induction of HSPs to improve outcome in human disease has not been exploited because laboratory induction agents are themselves toxic and not clinically relevant. Many researchers have found that glutamine (GLN), a conditionally essential amino acid, can enhance stress-induced HSP expression in vitro and improve cell survival against a variety of stressful stimuli. Further, recent data from me and my colleagues indicate that a single dose of intravenous GLN can enhance HSP expression, decrease end-organ injury, and enhance survival from septic shock in the intact rat. Thus GLN, which is beneficial in many settings of critical illness and injury, may be a clinically applicable enhancer of HSP expression. These results indicate that GLN could be used to enhance HSP expression and attenuate end-organ injury in situations when a major clinical stress is anticipated, such as before major surgical procedures (e.g., cardiac, vascular, and transplantation) or in the critically ill.
New developments in the fields of biochemistry, physiology, sepsis, cancer therapy, and molecular genetics have led to opportunities for the development of new therapies and prophylaxes for heat illnesses and for improving human performance during conditions of environmental stress. These include antilipopolysaccharide agents, anticytokines, potassium channel agents, a diet rich in omega-3 fatty acids, and psychological conditioning. This review summarizes the backgrounds and recent findings in the above fields and provides specific suggestions for potential therapy and prophylaxis for classic and exertional heatstroke and for improving athletic performance.
Three experiments were conducted to evaluate the effect of different management strategies on body temperature of feedlot steers finished in the summer months. In Exp. 1, 24 crossbred steers were chosen to assess the effect of altered feed intake and feeding time on tympanic temperature (TT) response. Managed feeding (MF) treatments were applied for 22 d only and provided 1) ad libitum access to feed at 0800 (ADLIB), 2) feed at 1600 with amount adjusted so that no feed was available at 0800 (BKMGT), 3) feed at 1600 at 85% of predicted ad libitum levels (LIMFD). During heat stress conditions on d 20 to 22 of MF, LIMFD and BKMGT had lower (P < 0.05) TT than ADLIB from 2100 through 2400. A carryover effect of limit-feeding was evident during a severe heat episode (d 36 to 38) with LIMFD steers having lower (P < 0.05) TT than ADLIB. In Exp. 2, TT were obtained from 24 crossbred steers assigned to three treatments, consisting of no water application (CON), water applied to feedlot mound surfaces from 1000 to 1200 (AM) or 1400 to 1600 (PM). From 2200 to 0900 and 1200 to 1400, steers assigned to morning sprinkling treatment had lower (P < 0.05) TT than steers assigned to afternoon sprinkling treatment. In Exp. 3, 24 steers were utilized in a 2 x 2 factorial arrangement of treatments with factors of feeding time [0800 (AMF) and 1400 (PMF)] and sprinkling (WET and DRY). Tympanic temperatures were monitored under hot environmental conditions on d 30 to 32 and 61 to 62. A feeding time x sprinkling interaction (P < 0.001) was evident on d 30 to 32, although AMF/DRY steers had the highest (P < 0.05) TT. On d 61 to 62, TT of PMF steers was higher (P < 0.05) than AMF between 1500 to 1800. Use of sprinklers can effectively reduce TT of feedlot cattle, whereas shifting to an afternoon vs morning feeding time was most beneficial when bunks were empty several hours prior to feeding.