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Abstract

The use of blankets in horses is widespread in Northern Europe. However, horses are very adaptable to low temperatures and the practice is questioned because blankets may hamper heat dissipation at high temperatures and also disturb free movement. The aim of the current study was to gain information about horses’ own preferences for wearing or not wearing a blanket under different weather conditions during the seasons. 10 horses usually wearing blankets and 13 horses usually not wearing blankets were kept outside in their paddock for 2 h during different weather conditions. Then, these horses were tested for their preference for wearing blankets (see Mejdell et al., 2016). When only considering air temperature and not the impact of other weather factors, the horses preferred to have the blanket on in 80% and 90% of the test at t < -10 °C in horses usually wearing and not wearing blankets, respectively. As air temperature increased, the preference for keeping the blanket on decreased and at air temperatures > 20 °C, the horses preferred to remove the blanket in all the tests. According to the statistical model, the probability for choosing to have a blanket on increased with increasing wind speed, and also precipitation increased the probability for choosing to have a blanket on. Sunshine however, reduced the probability for choosing to wear a blanket.

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... Because physiotherapeutic methods are usually quite time consuming, they seem unfeasible for long-term use (McGowan et al., 2007a) and it may be justified to seek new methods that can be used in practice. These methods can include body heating with blankets, especially in winter (Mejdell et al., 2019). Indications in such cases include thermoregulation disorders and generally weakened immunity of geriatric horses (Brosnahan and Paradis, 2003). ...
... The use of a blanket of appropriate thickness can help to optimize the thermoregulation processes which improve the general animal welfare (Mejdell et al., 2019). However, the use of a blanket may also have negative effects on the body, lead to overheating, or cause general discomfort for the animal. ...
... These findings suggest that the use of the thickest possible blankets in geriatric horses in winter is justified. It would be interesting to compare a study on geriatric horses with the findings of a study conducted by Mejdell et al. (2019) regarding the choice of a blanket to be worn by adult horses, although no such choice appears necessary for geriatric horses. ...
Article
This study analyzed the rectal and surface temperature of the horse’s body, its heart rate variability parameters and the step length when walking and trotting geriatric horses using blankets with various thermoinsulating properties. Twenty-four hot-blooded geldings were included in the study. The experiment was conducted in winter over a period of 30 consecutive days. The horses in the study were kept under three types of blankets (light, medium, thick). The control group was kept without blankets. The rectal and surface body temperature and the HRV parameters were measured before the experiment, immediately after the blankets were removed and an hour later. The step length when walking and trotting was measured before the experiment and the day before it was finished. The use of horse blankets in winter was found to have a positive effect on increasing the surface temperature of geriatric horses and thicker blankets produced more significant effects. For thick winter blankets, since one would expect an increase in the rectal temperature and elongation of the trotting step, it is recommended that they should be used at all times for geriatric horses prone to hypothermia and horses with painful muscles in the hind legs and the shoulder as the most common cause of reducing the length of the trotting step. The use of blankets should also result in a general body vitality improvement, which is demonstrated by a general increase in the activity of the autonomic nervous system, especially the sympathetic system.
... Additionally, higher wind speed causes an increase in the amount of time spent moving and higher humidity has been connected with a decrease in average lying time. However, these results, including those regarding the impact of temperature, were often dependent on additional circumstances including breed-type, age, or blanketing [26,27,28]. In addition, or possibly as a result, there have been several studies with conflicting results [18,20,28]. ...
... The younger horses may have had a lower tolerance to changes in the weather, and these correlations begin to fade as the horses age. This hypothesis was also proposed by Mejdell et al., who predicted the greater reactivity may result from a younger horse's heightened sensitivity to impaired hearing during strong winds and stormy weather [27]. Age variations within the herd may have also played a role. ...
... For example, farm B blanketed its horses and farm A did not. Blankets alter behavior in response to winter weather, masking breed-type sensitivities to colder temperatures and decreasing the percentage of time horses spend in shelters [26,27]. Blanketed horses also spend more time walking on temperate days than days with low temperatures and snow [27]. ...
Article
Keeping horses outdoors on pasture full-time with free access to shelter holds numerous advantages over housing in stalls, promoting both better mental and physical health. One reason for these benefits is the potential for increased physical activity in horses outdoors on pasture versus those confined to stalls. However, it is not guaranteed the horse will take advantage of this opportunity for greater movement. For this reason, it is important to understand the various reasons why horse activity patterns change. The objective of this study was to investigate how various weather factors - including temperature, humidity, precipitation, and wind speed - directly affect equine movement. To achieve this, horses on two similarly-managed farms were equipped with triaxial accelerometers during five independent time periods from January to August. These devices tracked number of steps, standing time, time lying down, and number of lying bouts. The movement data were then compared to the corresponding weather conditions. No strong correlations were found between the recorded movement of the horses and any of the environmental conditions. However, differences in average number of steps and average time lying down were observed between farms and across testing periods, suggesting other influences such as ground conditions and the use of blankets. Further studies are needed to determine the best management practices to encourage pasture activity and support optimal equine physical health.
... In another study, horses were trained to communicate their preferences for wearing blankets during different weather conditions (Mejdell et al., , 2019. No horses in that study indicated that they preferred to wear blankets in sunny spring and summer weather, and most asked for a blanket in chilly weather with rain and wind. ...
... This reflects individual difference that even the owners could not anticipate . Detailed analyses of the choices made in different weather conditions have later revealed that individual horses have different thresholds for when they choose to get a blanket on (Mejdell et al., 2019). ...
... Still, the interaction between horse type category and weather extremes on horse use of shelter indicate that the blanket was not enough to protect horses at inclement weather conditions. This may again be explained by the slight differences in thermal comfort that individual horses have displayed in the study by Mejdell et al (2019). ...
Article
Horses use human-made shelters actively during inclement weather, but the costs of building shelters may be high and owners use blankets or rugs on horses instead. The aim of the study was to investigate how wearing a blanket might affect the shelter seeking behaviour of horses under coastal arctic winter conditions. Could blankets make shelters redundant? During different winter weather conditions, seventeen horses had a full-neck blanket of their size put on and were released in a test paddock. There, horses were given free choice between staying outdoors, going into a heated shelter compartment or into a non-heated shelter compartment. An observer scored horse’s location and behaviour using instantaneous sampling every minute for 1 h. Each horse was tested 2–12 days but only once per day. Detailed weather data (precipitation, wind and temperature) were continuously recorded by a weather station at the site. In general, horses with blankets still used the shelter and were observed inside in (mean per horse) 20.6% of total observations. Horses spent more time inside shelters on days with rain and wind (39.7% of tot obs) compared to on days with wind only (11.8% of tot obs, P = 0.05). Small coldblood horses were more active, spending more time in movement than large coldblood and large warmblood horses (P = 0.01). In conclusion, wearing blankets reduced the impact of inclement weather, but did not make the shelter redundant for horses, under Nordic winter conditions.
... Horses kept outside or in non-insulated buildings will be exposed to a range of climatic conditions. In contrast to horse owners' assumptions, Mejdell et al. (2019) showed that horses generally preferred to be without a blanket during turnout at moderately cold and mild temperatures without precipitation and wind. Furthermore, acclimatized Icelandic horses have been kept outside in winter at temperatures ofof À 30 � C (range þ5 to À 30 � C), without health problems, behavioral signs of discomfort or increased secretion of thyroid hormones (Mejdell and Bøe, 2005). ...
... This objective measure, in addition to behavioral signs of thermal discomfort may be used before deciding on a blanketing regime. The results in Mejdell et al. (2019) also underlined that the need for extra protection is very individual. It is, however, important that the operator is trained and knows how to use the camera and interpret the images. ...
Article
Horse owners may lack knowledge about natural thermoregulation mechanisms in horses. Horses are managed intensively; usually stabled at night and turned out during the day. Some are clipped and many wear a blanket, practices which reduce the horse's ability to regulate heat dissipation. The aim of this study was to investigate the relationship between hair coat characteristics, body condition and infrared surface temperatures from different body parts of horses. Under standard conditions, the body surface temperature of 21 adult horses were investigated using infrared thermography. From several readings on the same body part, a mean temperature was calculated for each body part per horse. Detailed information on horse breed, age, management and body condition was collected. Hair coat samples were also taken for analyses. A mixed statistical model was applied. Warmblood horse types (WB) had lower hair coat sample weights and shorter hair length than coldblood horse types (CB). The highest radiant surface temperatures were found at the chest 22.5 ± 0.9 °C and shoulders 20.4 ± 1.1 °C and WB horses had significantly higher surface temperatures than CB horses on the rump (P < 0.05). Horses with a higher hair coat sample weight had a lower surface temperature (P < 0.001) and hind hooves with iron shoes had a significant lower surface temperature than unshod hind hooves (P = 0.03). In conclusion, individual assessment of radiant surface temperature using infrared thermography might be a promising tool to gather data on heat loss from the horses' body. Such data may be important for management advice, as the results showed individual differences in hair coat characteristics and body condition in horses of similar breeds.
... Horses distinctly preferred being ridden with a natural head position compared to a hyperflexed position [53]. Mejdell et al. [54] showed horses had a clear preference for wearing blankets in freezing temperatures. ...
Article
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Horses (Equus caballus) have been domesticated for millennia and are regularly utilized for work, sport, and companionship. Enhanced understanding of human–horse interactions can create avenues to optimize their welfare. This review explores the current research surrounding many aspects of human–horse interactions by first highlighting the horse’s sensory capabilities and how they pertain to human interactions. Evidence exists that suggests that horses can read humans in various ways through our body odours, posture, facial expressions, and attentiveness. The literature also suggests that horses are capable of remembering previous experiences when working with humans. The interrelatedness of equine cognition and affective states within the horse’s umwelt is then explored. From there, equine personality and the current literature regarding emotional transfer between humans and horses is examined. Even though horses may be capable of recognizing emotional states in humans, there remains a gap in the literature of whether horses are capable of empathizing with human emotion. The objective of this literature review is to explore aspects of the relationship between humans and horses to better understand the horse’s umwelt and thereby shed new light on potential positive approaches to enhance equine welfare with humans.
... Above 10°C, horses prefer not to be rugged except in extreme wet or windy weather conditions 10,11 ; if the weather is neither wet nor windy, rugs are only required below 5°C, and acclimatised horses may only require rugs below temperatures as low as -10°C. ...
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A MEETING of academics and practitioners with an interest in equine obesity and obesity-related laminitis was convened for Veterinary Times Equine (sponsored by Bova UK) on 14 January 2020. Published evidence was reviewed and opinions were shared to provide the following summary for veterinary surgeons managing horses with obesity.
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Blanketing is a highly debated practice utilized in the equine community as part of winter horse management. Despite this, little research is available on the prevalence, reasoning, and management decisions related to use of blankets for horses in North America. Therefore, the objective of this study was to develop an understanding of blanketing management practices and beliefs of North American horse owners. A 33-question, branched online survey was developed and available between December 1, 2020 and January 5, 2021 and advertised using social media and e-newsletters. The FREQ procedure for Chi-squared analysis in SAS was used when comparisons were made between participant-reported frequencies. There were 1,450 respondents from North America who completed the survey. Demographic information indicated the majority of respondents were from the Midwest region of the United States (68%); however, geographical region did not impact the frequency of blanket usage (P = 0.17, X² = 8.99). When respondents were asked to self-report discipline, recreational riding was the most prevalent (40%). Overall, 54% of respondents (n = 790) reported blanketing the majority of their horses during the winter. The most frequently selected reason respondents chose to blanket horses was exposure to precipitation (78%). Out of the respondents who did not blanket the majority of their horses (n = 660), the primary reason for not blanketing was access to shelter (50%). This survey provides valuable information on blanketing and winter management practices reported by horse caretakers in North America and will help direct future research and education efforts.
Article
In the Nordic countries, permanent outdoor housing of horses in winter is gaining popularity. This practice will expose the horses to harsh weather conditions. However, horses that are kept indoors at night and turned out in the cold during daytime also experience thermoregulatory challenges. With emphasis on the special challenges in a Nordic climate, this paper aims to increase the understanding of thermoregulation in horses, and ultimately to improve management practices. First, factors related to the environment and the mechanisms of heat exchange are summarised, thereafter the factors related to the horse, such as anatomy and physiological mechanisms which are important for balancing heat gain and heat loss. Human utility of horses and management practices such as clipping, the use of rugs, and provision of shelter are discussed in the light of thermoregulation in horses. The management and care for horses should take into account the principles of thermoregulation and mechanisms of heat loss and gain, and horses should be given a freedom of choice to cope with changing weather conditions. This should include space for movement, protection from sunshine, precipitation and wind, dry bedding, and appropriate feeding. Several studies indicate that the combination of cold rain and wind is a very demanding weather type, not just very low ambient temperatures. A shelter offers the horse protection from wind, precipitation and radiation which it can use when needed, and is therefore a more flexible management solution than a rug, especially when weather conditions change rapidly. In inclement weather, a rug may be a useful supplement. Too many horse owners clip their horse, which often necessitates the use of rugs on a regular basis. More knowledge is needed on how to best manage sport horses, especially when being sweaty after exercise in winter, to ensure good welfare.
Article
The objective of this study was to examine changes in surface temperature of blanketed horses during cold weather. Four mature stock-type horses were used in a 4 × 4 Latin square design. Treatments included 3 different blanket weights (based on g of fiberfill): light weight (LW; 0 g), medium weight (MW; 200 g), heavy weight (HW; 400 g), and a nonblanketed control (CON). Thermographic images were obtained from a standardized lumbar location before blanketing and immediately after cold exposure. During cold exposure, horses were outside with ad libitum access to grass hay and water for 1 hour. Mean temperature was -23°C with a wind chill of -32°C. After 1 hour, horses were brought inside (15°C) and lumbar images immediately recorded. A 30-minute equilibration period was allowed between each sampling period. Analysis of variance was computed using the general linear model procedure of SAS with statistical significance declared at P values ≤ 0.05. There was an overall treatment effect (P = .02) for lumbar temperatures after horses were outside for 1 hour with temperatures measuring 22.3°C, 26.8°C, 30.3°C, and 31.5°C for CON, LW, MW, and HW, respectively. Lumbar temperature was warmer (P ≤ .009) for HW and MW compared with CON and tended to be warmer (P = .10) in LW compared with CON. Change in lumbar temperature decreased significantly (P ≤ .01) in CON compared with all other treatments. In conclusion, wearing a blanket can increase lumbar surface temperature during cold weather with the degree of warmth influenced by blanket weight.
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This paper describes a method in which horses learn to communicate by touching different neutral visual symbols, in order to tell the handler whether they want to have a blanket on or not. Horses were trained for 10–15minutes per day, following a training program comprising ten steps in a strategic order. Reward based operant conditioning was used to teach horses to approach and touch a board, and to understand the meaning of three different symbols. Heat and cold challenges were performed to help learning and to check level of understanding. At certain stages, a learning criterion of correct responses for 8-14 successive trials had to be achieved before proceeding. After introducing the free choice situation, on average at training day 11, the horse could choose between a “no change” symbol and the symbol for either “blanket on” or “blanket off” depending on whether the horse already wore a blanket or not. A cut off point for performance or non-performance was set to day 14, and 23/23 horses successfully learned the task within this limit. Horses of warm-blood type needed fewer training days to reach criterion than cold-bloods (P<0.05). Horses were then tested under differing weather conditions. Results show that choices made, i.e. the symbol touched, was not random but dependent on weather. Horses chose to stay without a blanket in nice weather, and they chose to have a blanket on when the weather was wet, windy and cold (χ2=36.67, P<0.005). This indicates that horses both had an understanding of the consequence of their choice on own thermal comfort, and that they successfully had learned to communicate their preference by using the symbols. The method represents a novel tool for studying preferences in horses.
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Aims: The aims of the study were to investigate i) the kind of the relationship among BCS and subcutaneous fat thickness (FT) in horses, as affected by breed, gender and age, and ii) the effectiveness of a combination of the two variables in order to better estimate adiposity. Study design: Body weight (BW), FT (at croup level, by means of an ultrasound device) and BCS (5 point scale) were recorded in 124 horses (55 Standardbred; 25 Italian Saddler; 44 Thoroughbred) of different gender (95 mares; 14 stallions; 15 geldings) and age (26 ≤4 years of age; 98 >4 years of age) at five commercial herds. Methodology: After at least one hour from the morning meal, BW, by means of an electronic balance, and FT on the croup, at approximately 11 cm cranial to the tail head and 10 cm lateral to the midline, by means of an ultrasound device (Lean-Meater, Renco Corporation) were recorded. BCS was evaluated at the same moment on a scale of 1 to 5 (1 = emaciated and 5 = extremely obese). Results: BCS was affected by breed (P<.05), while FT was independent of breed, gender and age (P>.05). Overall FT and BCS were moderately correlated (r=0.335; P<.01); correlation coefficients were higher in Italian Saddler (r=0.549; P<.01), stallions (r=0.631; P<.05), and young horses (r=0.539; P<.01). A new variable (FT_BCS), calculated as (FT*BCS)/(FT+BCS), is proposed. It resulted correlated both to FT (r=0.754; P<.01) and BCS (r=0.824; P<.01). Allometric coefficients of FT and BCS on BW were of the same sign, regardless of sex and breed, as mature horses tended to decrease FT and increase BCS with the increase of BW; coefficients for FT_BCS on BW gave a better fit than FT or BCS alone, as in Thoroughbred and in young horses they gave a better fit than both FT and BCS. Conclusion: The study showed that, due to their correlation, BCS or FT alone could be not sufficient to describe horse body adiposity, but their association could be more useful; in the weight range between 470 and 500 kg, their combination is able to appreciate a deviation from linearity of the allometric equation with BW in geldings and Italian Saddler horses.
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Clipping the winter coat in horses is done to improve heat dissipation during exercise and make grooming easier. It is often combined with blanketing to keep the horse warm. The aims of the present study were to investigate how clipping and the use of blankets affect thermoregulation during exercise and recovery in horses. One Gotland pony, one New Forest pony, and one warm-blooded horse exercised one after the other on a 6450 m long track. The horses walked, trotted and cantered according to a predetermined scheme, which took about 50 minutes including three stops. The scheme was repeated on five consecutive days when horses were: 1) unclipped 2) unclipped + blanket during recovery, 3) left or right side clipped, 4) clipped, and 5) clipped + riding blanket + blanket during recovery. Heart rate (HR) was measured with telemetry, respiratory rate (RR) by counting flank contractions, skin temperatures by thermistor probes, and rectal temperature with a digital thermometer. Skin wetness (SW) was estimated by ocular inspection (dripping = 5, dry = 0). Mean outdoor temperature varied from -1.1 to - 8.7°C. HR increased progressively during exercise with no difference between treatments. Maximum RR was 77 ± 30 breaths/min (unclipped) and 49 ± 27 breaths/min (clipped). The lowest skin temperature was 17.5 ± 2.7°C in a hind leg during exercise, which increased to 34.5 ± 0.1°C during recovery. Rectal temperature was elevated during recovery in unclipped, but not in clipped horses and skin temperature at base of tail was elevated during recovery except in unclipped horses without blanket. Moisture after exercise scored 3.2 ± 0.8 in unclipped and zero in clipped horses. Leg skin temperature initially dropped at onset of exercise in clipped horses, and then increased after about 30 minutes due to internal heat from the working muscles. These changes were not significant when clipped horses had riding blankets, whereas unclipped horses became overheated as judged from respiratory rate and elevated rectal temperature. Providing clipped horses with blankets dampened the changes in leg skin temperature during exercise.
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Horses respond to chronic cold exposure by acclimatization or habituation. Acclimatized, adult horses have a lower critical temperature (LCT) of −15°C. Yearling horses have a LCT of −11°C if fed ad lib or 0°C if limit fed energy for moderate growth. Newborns have a LCT around 20°C. Horses, unlike cattle, do not respond to chronic cold exposure by increasing thyroid hormone secretion. Thyroid hormone secretion responds more to a lengthening photoperiod. Yet, in newborns, thyroid hormones are likely thermogenic. Metabolic rates increase by 70% above resting in severely cold stressed horses. Maintenance digestible energy (DE) intakes should be increased 2.5% per Celsius degree decrease in effective ambient temperature for adult horses and by 1.3% per degree decrease for growing horses fed for moderate gain at temperatures below LCT.
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Limited information is available on the extent to which blankets are used on horses and the owners’ reasoning behind clipping the horse’s coat. Research on the effects of those practices on horse welfare is scarce but results indicate that blanketing and clipping may not be necessary from the horse’s perspective and can interfere with the horse’s thermo-regulatory capacities. Therefore, this survey collected robust, quantitative data on the housing routines and management of horses with focus on blanketing and clipping practices as reported by members of the Swedish and Norwegian equestrian community. Horse owners were approached via an online survey, which was distributed to equestrian organizations and social media. Data from 4,122 Swedish and 2,075 Norwegian respondents were collected, of which 91 and 84% of respondents, respectively, reported using blankets on horses during turnout. Almost all respondents owning warmblood riding horses used blankets outdoors (97% in Sweden and 96% in Norway) whereas owners with Icelandic horses and coldblood riding horses used blankets significantly less (P < 0.05). Blankets were mainly used during rainy, cold, or windy weather conditions and in ambient temperatures of 10°C and below. The horse’s coat was clipped by 67% of respondents in Sweden and 35% of Norwegian respondents whereby owners with warmblood horses and horses primarily used for dressage and competition reported clipping the coat most frequently. In contrast to scientific results indicating that recovery time after exercise increases with blankets and that clipped horses have a greater heat loss capacity, only around 50% of respondents agreed to these statements. This indicates that evidence-based information on all aspects of blanketing and clipping has not yet been widely distributed in practice. More research is encouraged, specifically looking at the effect of blankets on sweaty horses being turned out after intense physical exercise and the effect of blankets on social interactions such as mutual grooming. Future efforts should be tailored to disseminate knowledge more efficiently, which can ultimately stimulate thoughtful decision-making by horse owners concerning the use of blankets and clipping the horse’s coat. © 2017 American Society of Animal Science. All rights reserved.
Article
Reasons for performing study: Horses may adapt to a wide range of temperatures and weather conditions. Humans often interfere with this natural thermoregulation ability by clipping and use of blankets. Objectives: To investigate the effects of different winter weather conditions on shelter seeking behaviour of horses and their preference for additional heat. Study design: Observational study in various environments. Methods: Adult (n = 22) horses were given a free choice test between staying outdoors, going into a heated shelter compartment or into a non-heated shelter compartment. Horse location and behaviour was scored using instantaneous sampling every minute for one hour. Each horse was tested once per day and weather factors were continuously recorded by a local weather station. Results: The weather conditions influenced time spent outdoors, ranging from 52% (of all observations) on days with mild temperatures, wind and rain to 88% on days with <0°C and dry weather. Shivering was only observed during mild temperatures and rain/sleet. Small Warmblood horses were observed to select outdoors less (34% of all observations) than small Coldblood horses (80%). We found significant correlations between hair coat sample weight and number of observations outdoors (ρ = 0,23; P = 0.004). Conclusions: Horses selected shelters the most on days with precipitation and horses changed from a non-heated compartment to a heated compartment as weather changed from calm and dry to wet and windy. Horse breed category affected the use of shelter and body condition score and hair coat weight were associated with voluntary shelter selection. This article is protected by copyright. All rights reserved.
Article
1.1. The thermal resistance of the hair coat from the torso of a Thoroughbred foal was determined in relation to its moisture content.2.2. When dry and combed, the thermal resistance of the coat was about 80s m−1. The thermal resistance of the dry coat decreased slightly with increasing air temperature (range 3 to 20°C).3.3. Moisture (about 350 g per unit surface area) reduced the coat resistance by two thirds, to about 25 s m−1. The wet coat took about 3 h to dry. During this period, the coat resistance increased with decreasing moisture content.4.4. After drying, the coat remained compressed and its resistance was only about 50 s m−1. Compression did not have a significant effect on the insulation per unit depth of hair.
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Metabolic rate was assessed at controlled environmental temperatures in six winter-acclimatized mature Quarter Horse geldings. Within an environmental chamber maintained at 18 °C, metabolic rate was similar (P > 0.05) at the beginning (November) and end (mid-January) of the trial. During periods of acute cold exposure (6 h), metabolic rate was found to be elevated (P < 0.05) at temperatures below −10 °C, increasing to 142% of basal metabolic rate values at −40 °C. At temperatures above 10 °C, metabolic rate tended to be elevated (P < 0.07) over basal levels recorded at 0 °C. Thyroid hormone responses to temperature were monitored by evaluating total plasma T 3 and T 4 in blood samples collected from the jugular vein. Basal plasma T 3 and T 4 concentrations were both observed to rise (P < 0.05) during the experiment while the horses were exposed to outdoor ambient temperature. Short-term cold exposure within the environmental chamber had no effect on either plasma T 3 or T 4 concentration (P > 0.05). These results indicate that the thermoneutral zone of the mature horse housed outdoors during winter ranges from approximately −15 °C to 10 °C. During this experiment, outdoor housing did not result in winter acclimatization, as reflected by the constancy of metabolic rate estimates, although changes in basal concentrations of T 3 and T 4 were observed. Key words: Horses, metabolic rate, thyroid hormones, temperature
Article
The scientific literature on adaptation to cold in the horse is scant. Yet, if one considers the geographical range of horse rearing around the world one can see that much of it lies in cold-climate zones or those with a cold winter. An examination of the literature on thermoregulation in mammals brings out a number of questions relevant to horse breeds. The answers to some of these questions may be of practical value in horse husbandry. An animal adapts to cold first and foremost by reducing thermolysis, and also by increasing thermogenesis. These are achieved through a variety of mechanisms, examined in this paper both in the individual animal and at the level of the population to which the individual belongs. Seasonal reproduction, for example, can be interpreted as a form of cold adaptation. The mechanisms involved often combine resistance to cold with resistance to food shortage, and body reserves play an important part. Aerobic metabolism, in which fatty acids are broken down, tends to take precedence over anaerobic metabolism, in which glycogen is broken down. The former is suited to prolonged, low-intensity effort, while the latter is suited to intense exertion of short duration. By examining all these phenomena one can work out the archetypes of the horse adapted to cold conditions and, conversely, those adapted to heat. These prove to match up quite well with the traditional classification into cold blood and warm blood. Most breeds can be placed somewhere between the two extremes. However, it is worth noting that the various breeds of trotters found in the cold climatic countries are the most northerly form of warm-blooded horses. Improving environmental conditions would therefore seem to have some economic limits.
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Background: Pituitary pars intermedia dysfunction (PPID) in older equids is commonly recognized by a long hair coat that fails to shed. Objective: The aim of this study was to compare hair follicle stages in PPID-affected horses with excessively long hair coats with the stages of normal aged horses (controls) and to compare hair follicle stages in PPID-affected horses after 6 months of treatment with pergolide mesylate with those of control horses. Animals: Eight PPID-affected horses and four normal, age-matched, control horses. Methods: Skin biopsies were collected from the neck and rump of PPID-affected and control horses. A diagnosis of PPID was established based on hair coat changes and supportive overnight dexamethasone suppression test results. Skin biopsies were repeated after 6 months of treatment with pergolide. The number of hair follicles in anagen (A) or telogen (T) was counted for each skin biopsy using transverse sections. Results: Pretreatment biopsies had a greater percentage of A follicles (neck 96%, rump 95%) and a lower percentage of T follicles (neck 4%, rump 5%) in PPID-affected horses than in control horses (A, neck 15%, rump 25%; and T, neck 85%, rump 75%). After treatment with pergolide, all PPID-affected horses had improved shedding, and the percentages of A follicles (neck 69%, rump 70%) and T follicles (neck 31%, rump 30%) were not different from untreated control horses (A, neck 68%, rump 82%; and T, neck 32%, rump 18%). Conclusions: These findings document that excessive hair growth (hypertrichosis) in PPID-affected horses is due to persistence of hair follicles in A. Furthermore, treatment with pergolide improved shedding and reduced the percentage of A follicles in PPID-affected horses.
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1.1. This short communication discusses the critical temperature and thermoneutral zone data for horses from the three earlier papers (Morgan, 1997a, 1997b; Morgan et al., 1997). Some practical aspects of climatory physiology of horses are also discussed.2.2. The baseline rate of total heat loss from horses, calculated by summing the rates of non-evaporative and evaporative heat loss, was 142 W m2−, and remained stable in ambient temperatures ranging from 5–25°C.3.3. The lower critical temperature was found to be 5°C. The upper critical temperature was proven to depend on what definition was chosen.
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Older horses have an increased risk of hyperthermia due to impaired cardiovascular function. While many studies have investigated thermoregulation in horses during exercise, none have investigated the effects of ageing. To test the hypothesis that there is a difference in thermoregulation during exercise and plasma volume (PV) in young and old horses. Study 1: 6 young (Y, 7.7 ± 0.5 years) and 5 old (O, 26.0 ± 0.8 years) unfit Standardbred mares (507 ± 11 kg, mean ± s.e.) ran on a treadmill (6% grade, velocity calculated to generate a work rate of 1625 watts) until core temperature reached 40 °C. Core (CT), skin (ST), rectal temperature (RT) and heart rate (HR) were measured every min until 10 min post exertion. Packed cell volume (HCT), lactate (LA) and plasma protein (TP) were measured in blood samples collected before, at 40 °C and every 5 min until 10 min post exercise. Sweat loss was estimated using bodyweight. Study 2: Plasma volume was measured in 26 young (8.2 ± 0.7 years) and 8 old (26.6 ± 0.7 years) Standardbred mares (515 ± 12 kg) using Evans Blue dye. Pre-exercise blood (rBV) and red cell (rRCV) volumes were calculated using PV and HCT. Data analysis utilised repeated measures ANOVA and t tests and data are expressed as mean ± s.e. Old horses reached 40 °C faster (998 ± 113 vs. 1925 ± 259 s; P < 0.05) with a greater HR at 40 °C (184 ± 6 vs. 140 ± 5 beats/min; P < 0.05) and greater sweat losses (P < 0.05). Heart rate did not differ (P > 0.05) post exercise. Age did not alter (P > 0.05) CT, ST, RT, LA, HCT or TP. Plasma volume was greater in Y vs. O horses (P < 0.05, 28.5 ± 1.4 vs. 24.1 ± 1.6 l) as was rBV (41.3 ± 2.0 vs. 35.3 ± 2.3 l) and rRCV (13.3 ± 0.6 vs. 11.1 ± 0.8 l). Ageing compromises the ability to handle the combined demand of exercise and thermoregulation in part due to decreased absolute pre-exercise PV.
Article
To describe the demographic and clinical characteristics, management practices, and owner perception of a population of geriatric horses, and to compare these data with findings in a group of younger horses. Original study. 218 horses. Data were collected via a survey tool from owners of 165 horses that were > or = 20 years of age and 53 horses that were < 20 years of age. Compared with young horses, the geriatric group included a significantly greater number of ponies; geriatric horses were also more likely to have a history of colic, dental disease, tumors, lameness, and pituitary disease, but not laminitis, diarrhea, allergies, respiratory tract disease, thyroid disease, or fractures. Horses that had participated in Western equestrian disciplines were more likely to have a history of lameness. Among old horses, those with pituitary dysfunction were more likely to have a history of laminitis than those without pituitary dysfunction. Geriatric horses were more likely to have long hair and shedding abnormalities than were younger horses. Owners perceived their horses as old at approximately 22 years of age. In horses older than 16.5 years of age, age was a negative factor in the purchase of horses. Geriatric and young horses share some similar health problems, but old horses have distinct health problems and veterinary medical requirements. The management and athletic history of horses may influence health as they age.
Demographic and clinical characteristics of geriatric horses: 467 cases (1989-1999)
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