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The effect of fiber characteristics on thermoregulatory responses and feeding behavior of heat stressed cows
Abstract
We examined the effect of replacing wheat hay with soy hulls on thermoregulatory responses and feeding behavior under summer condition in dairy cows. Milk yield, feed intake, meal size, and number, heart rate and heat production were similar in the two dietary groups. Visit duration and time spent eating were shorter, and body temperature was higher in the soy hulls fed cows. It was concluded that supplying soy hulls can enable cows subjected to heat load conditions to reduce the costs of feed ingestion. However, the contribution of this tool to the overall energy budget is rather small.
... Lactating dairy cows consuming soy hulls had greater RT compared with cows receiving wheat hay (Arieli et al., 2004). Heat is produced as a result of ruminal fermentation and metabolism of feed, and an increase in metabolic rate is associated with feeding (Conrad, 1985;NRC, 1996). ...
... Water intake was increased in dairy cows exposed to elevated Tamb (Sanchez et al., 1994). Feed intake was reduced in heat stressed dairy cows (Arieli et al., 2004) and the duration of eating events was reduced during acute and chronic heat stress (Hahn et al., 1990;Aoki et al., 2005). ...
... Water consumption is decreased at estrus (Lukas et al., 2008) and RuT is increased in fasting cows (Dale et al., 1954) . Compared with a high fiber diet, consumption of a low fiber diet increased rectal temperatures (Arieli et al., 2004). ...
Postpartum, Angus cows were used to evaluate changes in ruminal temperature (RuT) for the identification and prediction of estrus. Cows were administered RuT transmitting boluses and synchronized with PGF2α. Ruminal temperature and ambient temperature were recorded hourly. The onset of estrus was determined by HeatWatch. Estrus was determined as a RuT increase of ≥ 0.7°C for a 9 h period compared with the mean RuT during the 12 to 84 h before the start of the 9 h period. Cows predicted as estrous based on RuT were AI to Angus bulls, 8 to 16 h after the first hour of the 9 h period in which RuT increased ≥ 0.7°C. Ruminal temperature was evaluated during the 16 to 24 before and 24 to 32 h after the onset of estrus. The effect of ambient temperature (Tamb) on RuT was evaluated in postpartum, Angus cows. Cows were exposed to Tamb ranging from 12 to 37°C. Relationships among RuT, maximal Tamb (Tmax) and temperature humidity index (THI) were evaluated during 8 d in January, June, and August. Relationships between rectal temperature (RT), respiration rate (RR), Tmax, THI, and RuT were evaluated on two sequential days in August when Tmax was 37°C (HOT) and 28°C (WARM). Ruminal temperature was greater during the 9 h after the onset of estrus compared with the 16 to 24 h before and 24 to 32 h after the onset of estrus. Increased RuT at estrus occurred when onset of estrus was at 0100 to 0800, 0900 to 1600, 1700 to 0000 h. Time of day influenced RuT in the 9 h after the onset of estrus. Daily Tmax of ≥ 32°C increased the magnitude of diurnal variation in RuT and influenced RuT at estrus compared with when ambient temperature was < 32°C. Correct identification of estrous cows by a RuT increase of ≥ 0.7°C occurred in 61% to 93% of cows. Non estrous cows were identified as estrus by a RuT increase of ≥ 0.7°C in 16 to 73 % of cows. Pregnancy rate of cows AI based on RuT was 40% or greater and was not influenced by daily Tmax. When cows were exposed to Tmax ≥ 34°C or THI ≥ 87, RuT was increased compared with Tmax < 34°C or THI < 87, respectively. Ruminal temperature, RT, and RR were greater on the HOT day compared with the WARM day. Ruminal temperature was positively correlated with RT, RR, Tmax, and THI. These results indicate that the use of RuT has potential for estrous detection in cattle. Estrous detections systems that utilize changes in physiology are less subjective than visual observation of estrous behavior, require less time, and labor expense. A RuT based estrous detection system may increase the use of AI in the cow-calf industry. Insemination of cows to genetically superior bulls provides producers the opportunity to decrease the calving interval, increase the number and weight of calves, and enhance the profitability of a cowherd.
... Increase in evening rectal temperature, 0.4°C at upper critical temperature (25°C) and 0.9°C at 30°C compared to that at 20°C, indicates that cows at 25°C and 30°C during the daytime were exposed to mild and severe heat stress, respectively. It is generally regarded that body temperature 38.6°C as neutral and the 0.4°C increase in rectal temperature as mild heat stress for cows (Arieli et al. 2004). The significant reduction in feed DM intake in this study is also in line with a moderate and severe heat stressed at 25°C and 30°C. ...
... Additionally, elevated respiration rates and water intake, resulting from increased environmental temperatures, lead to concomitant reductions in feed DM intake (Sunagawa et al. 2002). Under the 0.4°C increase in rectal temperature, though provided with an extra cooling regime, feed intake of dairy cows was decreased (Arieli et al. 2004). Neutral detergent fiber and ADF intakes were also reduced (P < 0.01) up to 18% and 22%, respectively, with increasing chamber temperature. ...
Three late-lactation Holstein cows were used to determine the effects of environmental temperature on performance and energy partitioning. Each cow was housed in a respiratory chamber for 30 consecutive days and exposed to three different conditions of environmental temperature: (i) 20 degrees C and 20 degrees C (20 degrees C), (ii) 25 degrees C and 20 degrees C (25 degrees C), (iii) 30 degrees C and 25 degrees C (30 degrees C) during the day and night, respectively. The temperature was switched in an interval of 10 days. Humidity in the chamber was maintained at 55-65% through the entire experimental period. The daily mean as well as morning and evening rectal temperatures of Holstein cows increased linearly (P < 0.05) as chamber temperature increased. There was a significant linear reduction in dry matter (DM) intake (P < 0.05) and an increase in DM digestibility (P < 0.05). The response in milk yield, however, was not affected by heat stress. There were no significant differences among treatments for intake energy, heat production, net energy for lactation and net energy for gain. This results of this study disagreed with the assumption that late lactation cows gave priority to increasing body tissue at the expense of milk production under thermal stress.
... Thus, under heat stress conditions, high fibre diets make cows more heatstressed. It has also been suggested that feeding cows a diet containing high-quality NDF (low lignin concentration and high digestibility) instead of a diet with low-quality NDF can reduce the negative effects of heat stress on their productivity, body temperature, and feeding behaviour (Arieli et al., 2004;Soriani et al., 2013). Interventions that specifically reduce the lignin but not necessarily the NDF concentration in SDF cows' diets should be targeted for future research. ...
This study aimed to rank potential drivers of cow productivity and welfare in tropical smallholder dairy farms (SDFs) in Vietnam. Forty-one variables were collected from 32 SDFs located in four geographically diverse dairy regions, with eight SDFs per region. Twelve variables, including milk yield (MILK), percentages of milk fat (mFA), protein (mPR), dry matter (mDM), energy-corrected milk yield (ECM), heart girth (HG), body weight (BW), ECM per 100 kg BW (ECMbw), body condition score (BCS), panting score (PS), inseminations per conception (tAI), and milk electrical resistance (mRE) of cows, were fitted as outcome variables in the models. Twenty-one other variables describing farm altitude, housing condition, and diet for the cows, cow genotypes, and cow physiological stage were fitted as explanatory variables. Increased farm altitude was associated with increases in ECM and mRE and with decreases in PS and tAI ( P < 0.05). Increases in roof heights and percentage of shed side open were associated with increases in ECM, mFA, and mDM ( P < 0.05). Increased dry matter intake and dietary densities of dry matter and fat were associated with increased MILK, ECM, and ECMbw and decreased tAI ( P < 0.05). Increased dietary lignin density was associated with increased PS. Increased genetic proportion of Brown Swiss in the herd was associated with increased MILK, ECM, and ECMbw ( P < 0.05). Thus, to improve cow productivity and welfare in Vietnamese SDFs, the following interventions were identified for testing in future cause-effect experiments: increasing floor area per cow, roof heights, shed sides open, dry matter intake, dietary fat density, and the genetic proportion of Brown Swiss and decreasing dietary lignin density.
... Los ambientes tropicales ofrecen ventajas y desventajas para la producción animal; dentro de los aspectos positivos se menciona que la precipitación alta y la duración solar diaria casi constante, favorecen la producción de forraje durante gran parte del año. En cambio, las desventajas están asociadas a: la proliferación de parásitos internos y externos (Jiménez et al., 2007); las enfermedades (White et al., 2003); los contenidos altos de pared celular en los forrajes que favorecen la producción de calor interno (Sánchez, Villareal y Soto, 2000;Arieli et al., 2004); y las temperaturas y humedad relativa altas, que conducen a una situación de estrés calórico afectando la expresión del potencial genético al comprometerse su bienestar (Kadzere et al., 2006). ...
Antecedentes:
Las estrategias de desarrollo agropecuario deben estar respaldadas por el conocimiento de las características agrometeorológicas que es un factor determinante en los procesos productivos.
Objetivo
. Analizar las condiciones climáticas en la Empresa Pecuaria Genética que tiene el principal rebaño de ganado Criollo cubano y su posible relación con el desenvolvimiento en pruebas de comportamiento.
Métodos: S
e dispuso de la información de 1 375 animales que realizaron su prueba durante el periodo 1982-2015 después que la base fue depurada. El peso final se ajustó a 540 días (PFA) y se dispuso también de la ganancia media diaria (GMD) y el peso por edad (PPE). Se contó con los registros mensuales de la temperatura mínima (Tmin), media (Tmed) en ⁰C, humedad relativa (HR) en % y se generó el índice temperatura-humedad (ITH). Mediante análisis de varianza y ecuaciones de regresión se analizó el comportamiento de las variables climáticas por mes y año, el comportamiento del PFA, GMD y PPE a través del tiempo y sus relaciones con las variables climáticas.
Resultados:
Las medias generales y las desviaciones estándar fueron: 19,19 ± 0,87 ⁰C; 24,51 ± 0,63 ⁰C; 78,64 ± 2,66 %; 74,23 ± 0,99 para Tmin, Tmed, HR e ITH, respectivamente. Todas las variables estuvieron influidas (P≤0,001) por el mes y año de inicio de las PC y las medias para la prueba: 334,43 ± 39,59 kg; 494,21 ± 107,81 g/día; 610,90 ± 77,25 g/día para PFA, GMD y PPE, respectivamente. Todas las variables fueron afectadas (P≤0,001) por el mes, año de inicio y el ITH. Las ecuaciones de regresión más precisas con R² > 94% fueron entre PFA-ITH y PPE-ITH.
Conclusiones:
Hay una tendencia clara a un empeoramiento de las condiciones climáticas a través del tiempo, así como los indicadores de las PC. Estas se desarrollan bajo condiciones de alerta climática resultando solo favorables cuando se iniciaron en el primer trimestre del año y diciembre.
... Los ambientes tropicales ofrecen ventajas y desventajas para la producción animal; dentro de los aspectos positivos se menciona que la precipitación alta y la duración solar diaria casi constante, favorecen la producción de forraje durante gran parte del año. En cambio, las desventajas están asociadas a: la proliferación de parásitos internos y externos (Jiménez et al., 2007); las enfermedades (White et al., 2003); los contenidos altos de pared celular en los forrajes que favorecen la producción de calor interno (Sánchez, Villareal y Soto, 2000;Arieli et al., 2004); y las temperaturas y humedad relativa altas, que conducen a una situación de estrés calórico afectando la expresión del potencial genético al comprometerse su bienestar (Kadzere et al., 2006). ...
... Diet also has an impact on the response of dairy cows to heat stress: overall its effects on saving metabolic heat production by supplementing saturated fatty acids [96,97], reducing neutral detergent fibre on a dry matter basis [98][99][100] and increasing the proportion of digestive fibre [101] have been studied. Indeed, replacing low quality NDF in diets by NDF of better quality (low lignin concentrations and high digestibility) modifies the effects of heat stress on performance, body temperature, rumination activity and feeding behaviour [100,102,103]. The above strategies must be applied with caution as they can increase the risk of rumen acidosis in reducing fibre. ...
Introduction
Projected temperature rise in the upcoming years due to climate change has increased interest in studying the effects of heat stress in dairy cows. Environmental indices are commonly used for detecting heat stress, but have been used mainly in studies focused on the productivity-related effects of heat stress. The welfare approach involves identifying physiological and behavioural measurements so as to start heat stress mitigation protocols before the appearance of impending severe health or production issues. Therefore, there is growing interest in studying the effects of heat stress on welfare. This systematic review seeks to summarise the animal-based responses to heat stress (physiological and behavioural, excluding productivity) that have been used in scientific literature.
Methods
Using systematic review guidelines set by PRISMA, research articles were identified, screened and summarised based on inclusion criteria for physiology and behaviour, excluding productivity, for animal-based resilience indicators. 129 published articles were reviewed to determine which animal-based indicators for heat stress were most frequently used in dairy cows.
Results
The articles considered report at least 212 different animal-based indicators that can be aggregated into body temperature, feeding, physiological response, resting, drinking, grazing and pasture-related behaviour, reactions to heat management and others. The most common physiological animal-based indicators are rectal temperature, respiration rate and dry matter intake, while the most common behavioural indicators are time spent lying, standing and feeding.
Conclusion
Although body temperature and respiration rate are the animal-based indicators most frequently used to assess heat stress in dairy cattle, when choosing an animal-based indicator for detecting heat stress using scientific literature to establish thresholds, characteristics that influence the scale of the response and the definition of heat stress must be taken into account, e.g. breed, lactation stage, milk yield, system type, climate region, bedding type, diet and cooling management strategies.
... Los ambientes tropicales ofrecen ventajas y desventajas para la producción animal; dentro de los aspectos positivos se menciona que la precipitación alta y la duración solar diaria casi constante, favorecen la producción de forraje durante gran parte del año. En cambio, la proliferación de parásitos internos y externos (Jiménez et al. 2007); las enfermedades; los contenidos altos de pared celular en los forrajes (Sánchez et al. 2000) que favorecen la producción de calor interno (Arieli et al. 2004); las temperaturas y HR altas, son condiciones que afectan la expresión del potencial genético de los animales (Kadzere et al. 2002), comprometen su bienestar (Tapki y Şahin 2006) y conducen a una situación de estrés calórico. ...
... Esses resultados estão diferentes dos achados de Reyes et al. (2007), que registraram concentração de gordura de 2,9 e 3,2% no leite de vacas holandesas de alta produção criadas em clima desértico com acesso à sombra, e à combinação de sombra + aspersão de água disponível por oito horas ao dia, respectivamente, inferindo que em condições ambientais de temperatura do ar superior a 40ºC, a promoção do conforto térmico animal influencia positivamente no conteúdo gorduroso do leite. Arieli et al. (2004), avaliando a composição química do leite de vacas holandesas com produção de aproximadamente 40kg leite vaca/dia, submetidas ao resfriamento por aspersão + ventilação antes da ordenha, verificaram percentual médio de gordura entre os tratamentos pesquisados de 3,13%. Já Silva et al. (2009), obtiveram percentuais de gordura láctea de 3,79 e 3,69 para animais à sombra e ao sol, respectivamente. ...
The objective of the present study were apprise in two environments in first milking upon production, composition, SCC of milk and the concentration hormonal plasmatic in cows Brown Swiss cattle in two-production level and system created biodynamic. We used 32 cows; we had 16 in low and 16 in up production. The cow waits 1.5 hour for the first milking on the sun and in without sun. All the cows had the loggers to register the environment variations. The design experimental was completely randomized with 2 x 2 arrangement factorial (two environments first milking and two levels of production), consisted of 4 groups of 8 repetitions each. The acidity (P≤0.01) and the total solids (P>0.05) were less in the milk from the cows put in without sun. The cows about the production less level showed acidity (P≤0.01), density (P>0.05), lactose (P≤0.01) and solids without lipids (P≤0.01) in the milk in cows form milk had low production therefore we did not observation some difference in total solids (P>0.05) between two level production. The SCC milk did not showed variations between the environments and the production level (P>0.05), therefore in the number, were up in the cows with of sun and when had low production. The values form T3, T4 and cortisol, not had variations in the four groups in the study (P>0.05) and was in accord with the literature. When we put the cows Brown Swiss cattle for 1,5 hours in the first milking in system created biodynamic of production showed low influence weather in the cows did not showed good up production and good milk composition.
... Los ambientes tropicales ofrecen ventajas y desventajas para la producción animal; dentro de los aspectos positivos se menciona que la precipitación alta y la duración solar diaria casi constante, favorecen la producción de forraje durante gran parte del año. En cambio, la proliferación de parásitos internos y externos (Jiménez et al. 2007); las enfermedades; los contenidos altos de pared celular en los forrajes (Sánchez et al. 2000) que favorecen la producción de calor interno (Arieli et al. 2004); las temperaturas y HR altas, son condiciones que afectan la expresión del potencial genético de los animales (Kadzere et al. 2002), comprometen su bienestar (Tapki y Şahin 2006) y conducen a una situación de estrés calórico. ...
Con el objetivo de evaluar el efecto del ambiente sobre la producción láctea diaria de un hato puro de la raza Jersey, aclimatado al trópico húmedo desde su nacimiento, se analizó los registros de producción de 26 animales y sus respectivas lactancias. Las 4 130 observaciones analizadas incluyeron: la identificación de la vaca; el día de pesa de la leche; el mes; el año; la producción de leche diaria; el día de lactancia respectivo; el número de parto; la edad del animal; las temperaturas máxima y mínima; la precipitación; la radiación solar; y la humedad relativa máxima y mínima. Los días de lactancia, el número de lactancias (3a-5a), la edad del animal (7,5-10 años) y el número de parto tuvieron un efecto altamente significativo sobre la producción de leche diaria. Con las variables ambientales se obtuvo que la precipitación >40 mm.día-1 y la humedad relativa <80%.día-1 (p<0,001) presentan un efecto directo sobre la producción de leche y que tanto la temperatura ambiental (p=0,32), como la radiación solar (p=0,31) y sus interacciones, tuvieron un efecto significativo. Finalmente, el incremento en la producción de leche debido a la precipitación diaria ronda 1,0 l.día-1.animal-1, mientras que la merma en producción promedio con relación a la humedad relativa (HR) alcanza hasta 1,75 l.día-1.animal-1.
Heat stress generally leads to a decrease in voluntaryintake, in relation to thermoregulation, in order to allow a decrease in heat production, especially due to rumenfermentations. The decrease in intake may also be due to a low availability of forage on rangelands, as well as itslow nutritive value and sometimes to a lack of drinking water. When feed intake is very low, digestibility may decrease, for one same diet. In controlled conditions andfor a same intake, an increase in temperature increases diet digestibility by 0.2 point per degree Celsius. To prevent the negative effects of heat stress, especially on feed intake, ruminants modify their intake pattern by grazing during the night when the temperature is at its lowest, by increasing the number of meals and decreasing their length. They also modify feed preferences and thus the composition of their diet. In intensive systems, it is suggested to provide a shelter, to use water mist, to increase the energy concentration of the diet, to provide a source of fermentable nitrogen when this may limit forage digestion, and to increase the cation-anion balance ofthe diet.
Two experiments were conducted using lactating Friesian-Holstein cows to measure the effects of heat stress, using temperature-humidity index (THI), on milk production, milk composition and dry matter intake (DMI) under the Mediterranean climate. These trials were carried out in two periods differing in average THI values (68 +/- 3.75 vs. 78 +/- 3.23 for the spring and summer periods, respectively). Daily THI was negatively correlated to milk yield (r = -0.76) and feed intake (r = -0.24). When the THI value increased from 68 to 78, milk production decreased by 21% and DMI by 9.6%. Milk yield decreased by 0.41 kg per cow per day for each point increase in the THI values above 69. Milk fat (3.24 vs. 3.58%) and milk protein (2.88 vs. 2.96%) were lower for the summer group. THI was positively correlated to respiration rate (RR) (r = 0.89), heart rate (HR) (r = 0.88), rectal temperature (RT) (r = 0.85) and cortisol (0.31), and negatively with free thyroxin (-0.43). As the THI values increased from 68 to 78, RT increased by 0.5degreesC, HR by 6 beats, and RR by 5 inspirations per min. The average concentration of cortisol increased from 21.75 to 23.5 nmol.L-1 (P > 0.05), while that of free thyroxin decreased from 15.5 to 14.5 pmol.L-1, (P > 0.05). Summer heat stress reduced milk yield and DMI, altered milk composition and affected the physiological functions of confined lactating Holstein cows managed under Mediterranean climatic conditions.
We examined whether heart rate (HR) could be used to estimate energy expenditure (EE) in cattle. Six Hereford heifers (345 +/- 10.8 kg BW) 12 mo of age were implanted with HR radio transmitters and maintained in individual pens under the following treatments: 1) shade or sun exposure, 2) high- or low-energy diet, and 3) feeding in morning or afternoon. The HR of animals was measured every .5 h during 3 mo; measurements of oxygen consumption and HR were made simultaneously in the morning and in the afternoon while animals were resting and exercising. Average daily HR (52 +/- 4 beats/min) and average daily EE (380 +/- 9 kJ/kg(.75)) in animals on the low-energy diet were less than values in animals on the high-energy diet (94 +/- 4 beats/min and 653 +/- 9 kJ/ kg(.75), respectively). For each animal and within each diet, linear regressions best described the relationship between HR and EE in resting animals, whereas quadratic regressions best described this relationship for exercising animals. The quadratic equation for the exercising animals could also be used for resting animals. In addition, a constant value of EE per heart beat (EE pulse) for each individual resting animal was found and gave accurate estimations. This method was convenient because 1) no exercise equipment was needed to generate the regression equations and 2) EE pulse was less affected by diet than was EE estimated by regression equations. We conclude that HR, a relatively easy measurement, can be useful and accurate in estimating EE. To increase the accuracy of the estimation of EE by HR, the relationship of HR to EE should be established for each animal. In addition, the nutritional regimen for the animal in which EE is estimated should be used for the animal in establishing the relationship.
Heat stress results from the animal's inability to dissipate sufficient heat to maintain homeothermy. Environmental factors, including ambient temperature, radiant energy, relative humidity, and metabolic heat associated with maintenance and productive processes, contribute to heat stress. The focus of this article is to identify environmental and metabolic factors that contribute to excessive heat load, describe how disruption of homeothermy alters physiologic systems of the cow, and discuss nutritional modifications that help to maintain homeostasis or prevent nutrient deficiencies that result from heat stress. Changes in diet are needed during hot weather to maintain nutrient intake, increase dietary nutrient density, or to reestablish homeostasis. Formulation for adequate nutrient intake is challenging because of the competition between nutrient density and other needs for the cow, including energy density and adequate dietary fiber. Lower DMI during hot weather reduces nutrients available for absorption, and absorbed nutrients are used less efficiently. An excess of degradable dietary protein is undesirable because of energy costs to metabolize and excrete excess N as urea. Optimizing ruminally undegraded protein improves milk yield in hot climates. Mineral losses via sweating (primarily K) and changes in blood acid-base chemistry resulting from hyperventilation reduce blood bicarbonate and blood buffering capacity and increase urinary excretion of electrolytes. Theoretical heat production favors feed ingredients with a lower heat increment, such as concentrates and fats, whereas forages have a greater heat increment. Improved dietary energy density and the lower heat increment associated with the inclusion of dietary fat must be coupled with limitations to fat feeding to avoid ruminal and metabolic disorders. Numerous nutritional modifications are used for hot weather feeding; however, many need further investigation to achieve specific recommendations.
Heat stress results from the animal's inability to dissipate sufficient heat to maintain homeothermy. Environmental factors, including ambient temperature, radiant energy, relative humidity, and metabolic heat associated with maintenance and productive processes, contribute to heat stress. The focus of this article is to identify environmental and metabolic factors that contribute to excessive heat load, describe how disruption of homeothermy alters physiologic systems of the cow, and discuss nutritional modifications that help to maintain homeostasis or prevent nutrient deficiencies that result from heat stress. Changes in diet are needed during hot weather to maintain nutrient intake, increase dietary nutrient density, or to reestablish homeostasis. Formulation for adequate nutrient intake is challenging because of the competition between nutrient density and other needs for the cow, including energy density and adequate dietary fiber. Lower DMI during hot weather reduces nutrients available for absorption, and absorbed nutrients are used less efficiently. An excess of degradable dietary protein is undesirable because of energy costs to metabolize and excrete excess N as urea. Optimizing ruminally undegraded protein improves milk yield in hot climates. Mineral losses via sweating (primarily K) and changes in blood acid-base chemistry resulting from hyperventilation reduce blood bicarbonate and blood buffering capacity and increase urinary excretion of electrolytes. Theoretical heat production favors feed ingredients with a lower heat increment, such as concentrates and fats, whereas forages have a greater heat increment. Improved dietary energy density and the lower heat increment associated with the inclusion of dietary fat must be coupled with limitations to fat feeding to avoid ruminal and metabolic disorders. Numerous nutritional modifications are used for hot weather feeding; however, many need further investigation to achieve specific recommendations.
The potential of soybean hulls (SH) to replace forage neutral detergent fiber (NDF) in total mixed rations (TMR) of lactating cows was examined. Forty lactating cows were divided into two groups and individually fed ad libitum one of two experimental diets for 8 weeks: (I) a TMR containing 18% forage NDF, corn silage (CS TMR); and (II) a similar TMR in which the corn silage component (16.5% of dry matter, DM) was replaced by SH (SH TMR), containing only 12% forage NDF. Total NDF content was 39 and 36% in the SH TMR and CS TMR, respectively. The SH group tended (P=0.09) to eat more NDF than the CS group, but DM intake was not influenced. Average milk fat yield was higher (P=0.04) in the SH group. Findings were supported by the extent of in vitro digestibility data showing higher digestibility (P
A real-time control system for individual food intake of group-housed dairy cows was designed and implemented. The system consists of 40 feeding stations, each position comprising an automatic opening and closing yoke-gate. The specially designed electro-pneumatic yoke-gate combines off-the-shelf identification, weighing and control systems in a unique mechanical implementation. The yoke-system enables real-time control of food intake, which can be specified for each cow, and for each station through an interactive user interface. In addition, the system enables measurement and utilization of on-line data related to individual food intake and feeding behavior information such as food access frequency, meal duration, intake rate and food quantity for each visit of a cow kept in the group. The advantages of this design are: (i) the system is based on commercial components, (ii) simplicity and high reliability resulting in low maintenance, and (iii) continuous measurement of all feeding parameters, including during the meal. Although the yoke-system was built for a research institute, it is a step towards a commercial system.
Two aspects of thermal losses which arise as a result of the metabolism of ruminants are reviewed. The first considers the energy costs associated with basal metabolism, with emphasis on the contribution of protein turnover. The heat production associated with protein synthesis in the mature maintenance fed ruminant accounts for a minimum of 15-20% of total heat loss. From the few data available from growing ruminants, protein synthesis accounts for a similar proportion of thermal loss here also. Secondly the problem of poor utilisation of some roughages compared with concentrates is discussed and comparisons made of the possible differences in energy costs of ingestion, digestion, including fermentation and absorption. It is concluded that differences in these processes are insufficient between the two types of ration to account for the larger thermal losses with roughages and it is suggested that the major cause is a differential ability to handle excess acetate. In animals fed concentrate diets the larger production of propionate supplies adequate NADPH2 to enable acetate to be converted to fat while in those fed roughages the larger amount of acetate and smaller proportion of propionate results in a metabolic excess of acetate which has to be eliminated as heat by some form of futile cycle. It is suggested that ruminants might be able to utilise efficiently larger quantities of acetate from roughage feeds provided an additional source of reduced coenzyme is available; such a source could well be amino acids.
Effects of diet forage-to-concentrate ratio and intake on balances of energy and nitrogen and portal-drained viscera (PDV), liver and kidney blood flow and O2 consumption were measured in seven growing beef heifers. Isonitrogenous pelleted diets containing approximately 75% alfalfa or 75% concentrate were fed daily as 12 equal meals every 2 h at two isoenergetic metabolizable energy intakes. A split-plot design was used, with 4 wk for adaptation to diet followed by 3-wk intake periods within 6-wk diet periods. Heifers consumed and digested less dry matter, energy and nitrogen when fed the 75% concentrate vs. 75% alfalfa diet at equal metabolizable energy. Heifers fed the 75% concentrate diet produced less heat energy and retained more tissue energy than when fed the 75% alfalfa diet. Blood flow for PDV, liver and kidneys increased with intake and was greater when heifers were fed the 75% alfalfa vs. 75% concentrate diet. Increased PDV and liver O2 uptake accounted for 44 and 72% of heat increment for the 75% concentrate and 75% alfalfa diets, respectively. Greater PDV uptake of O2 accounted for 72% of the decrease in tissue energy of heifers fed the 75% alfalfa vs. 75% concentrate diet at equal metabolizable energy.
Sixteen Holstein cows in midlactation were used in a 4 x 4 Latin square design to determine the effect of replacing alfalfa neutral detergent fiber (NDF), with NDF from a combination of whole linted cottonseed, dried distillers grains, and wheat middlings. The four diets were a basal control diet that was low in forage and fiber [(5.9 g of corn silage NDF and 6.1 g of alfalfa NDF/100 g of dry matter (DM)], a normal forage diet (low forage plus 10 g of additional alfalfa NDF/100 g of DM), and two low forage diets with either 5 or 10 g of NDF from the nonforage fiber sources added per 100 g of DM. Milk yield, milk protein yield, and milk protein percentage were higher, and milk fat percentage and fat yield were lower, for cows fed the low forage diets than for those fed the alfalfa control diet that was higher in fiber. Among the low forage diets, dry matter intake, milk fat percentage, and fat yield all increased linearly as NDF content increased. The ratio of acetate to propionate in the rumen and rumination times were greater for the normal forage control diet than for the high nonforage fiber diet. Added NDF from these nonforage fiber sources increased milk fat percentage and yield, but this increase was less than the NDF from alfalfa and less than predicted. In agreement with results of similar previous trials, milk protein yield and percentage were increased when alfalfa NDF was replaced with fiber from nonforage fiber sources.
Lactating dairy cows were used in experiments to determine the effects of feeding a combination of fibrous by-products to replace a portion of alfalfa hay or grain. Cows were fed a control diet, consisting of alfalfa hay, corn, soybean meal, and corn silage or one of four treatment diets. In these diets, a combination of soy hulls, corn gluten feed, and wheat midds replaced approximately 30 or 60% of alfalfa hay or 25 or 50% of corn and soybean meal. A 56-d production study used 50 midlactation dairy cows in a randomized complete block design. No differences in milk production or composition among treatments were measured, except for the diet in which 60% of the alfalfa hay was replaced with fibrous by-products. Cows fed this diet had a significantly lower percentage of milk fat compared with other treatments. A fermentation study used five fistulated, multiparous lactating dairy cows in a 5 x 5 Latin square design. Cows were fed one of the five experimental diets used in the production study during five consecutive 14-d periods. Rumen acetate to propionate ratio was highest for the control and 50% concentrate replacement diets (3.27) and lowest for the 60% hay replacement diet (2.78). This shift in ruminal volatile fatty acid profile corresponded to the change in milk fat percentage, measured during the production study. A mixture of fibrous by-products fed as an alternative to hay or grain ingredients could potentially decrease feed costs without a resultant decrease in milk production by mid-lactation dairy cows.
Animal and Human Calori-metry
- J A Mclean
- G Tobin
McLean, J.A., Tobin, G., 1990. Animal and Human Calori-metry. Cambridge University Press, Cambridge.
Nutrient Requirements of Dairy Cattle. 7th revision Dietary-induced thermo-genesis and feed evaluation in ruminants
- Dc Orskov
- E R Macleod
NRC, 2001. Nutrient Requirements of Dairy Cattle. 7th revision. National Academy of Science, Washington, DC. Orskov, E.R., MacLeod, N.A., 1990. Dietary-induced thermo-genesis and feed evaluation in ruminants. Proc. Nutr. Soc. 49, 227–237.
Effect of diet forage to concentrate ratio and intake on metabolism of growing beef heifers
- Reynolds