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The study was carried out on milk from cold-blooded Sokólski mares and warm-blooded Polish Halfbred mares. Milk samples were analysed for content of solids, protein, fat, lactose, and ash; density; energy value; percentage of α-lactalbumin (α-La), β-lactoglobulin (β-Lg), serum albumin (SA), immunoglobulin (Ig), lactoferrin (Lf) and lysozyme (Lz) in the total protein; and fatty acid profile. Milk from cold-blooded mares was found to be similar in protein and fat content to that of warm-blooded mares, but had higher content of solids, including lactose and ash. It also had significantly (P≤0.01) higher content of α-La, SA and Lz, and lower content of β-Lg, Ig and Lf in comparison to milk from warm-blooded mares. Milk from Sokólski horses had a significantly (P≤0.01) higher proportion of SFA, including C10:0, C12:0, C14:0, C16:0 (P≤0.01) and C18:0 (P≤0.05), while the milk of warm-blooded mares had a significantly (P≤0.01) higher proportion of MUFA, including C16:1n-9 and C18:n-9, and PUFA, including C18:2n-6 and C18:3n3. The share of n-6 and n-3 PUFA was significantly (P≤0.01) higher in milk from warm-blooded horses, but their ratio (n-6/n-3) was lower (more favourable) in milk from cold-blooded mares. In addition, milk from warm-blooded horses had a lower (P≤0.01) share of HSFA and a higher proportion of DFA compared to cold-blooded horses, as well as lower values for AI and TI. Despite these minor differences in comparison with warmblooded mares (Polish Halfbred), milk from cold-blooded Sokólski mares was shown to be a food product of high nutritional value, which is one argument in favour of the use of this horse breed for dairy purposes.

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.

This study analyzed heart rate variability (HRV) parameters in selected intervals of a 24-hour recording session. The study was conducted with eight young and eight old, clinically healthy geldings. HRV measurements were taken with Polar RS800CX instruments. The recordings were then analyzed with Kubios HRV software. The following time intervals were identified: 24 hours, 15 hours of the day (light period), 9 hours of the night in total, and in subsequent hours of the night. During each interval, the following time analysis parameters were investigated: heart rate (beats per minute; HR), verified beat-to-beat times (NN), standard deviation of the NN intervals (SDNN), and the square radical of the mean sum of the squares of differences between the adjacent NN intervals (rMSSD). The following HRV frequency parameters were also investigated: total power of the spectrum (TP), high-frequency spectrum (HF), low-frequency spectrum (LF), and LF/HF ratio. It was found that geriatric horses had higher HRs but reduced some HRV parameters compared to young horses. Noticeable changes were least evident after midnight, especially between 0100 h and 0400 h.

The aim of the study was to determine the internal and surface temperature of selected body parts of horses during their stay in paddocks in various weather conditions in the summer. The study was conducted on 10 adult thoroughbred mares. The experiment was carried out on horses spending time in the paddock in four eight-hour stages with differing weather conditions in summer (sunny, cloudy, rainy and windy). Measurements of internal temperature (Veterinär SC 12 veterinary thermometer) and surface temperature of the head, rib area and croup (Thermal Imagers Ti9 FLUKE infrared camera and SmartView 4.1 software) were carried out at rest and again after four and eight hours in the paddock. It was concluded that the time horses spend in the paddock in summer should depend on weather conditions. Many hours spent outside the stable during sunny weather accompanied by high air temperature can contribute to overheating. On the other hand, rain and wind can cause hypothermia. Therefore, it is worth considering leaving horses in the stable or limiting their stay in the paddock to no more than four hours.

This study analysed the effect of the sex of the horses as well as the type of their maintenance and use at the centre on the behavioural and physiological expression of short-term social isolation, which was assessed on the basis of heart and respiratory rates. A total of 27 clinically healthy horses were examined. The horses had social contact of various durations, were used with different regularity and were not equally accustomed to isolation. An isolation test was conducted. The heart and respiratory rates were measured at rest and after isolation, and the differences between the values were calculated. Moreover, points were assigned for the effect of isolation. The behaviour in subsequent stages of isolation was also observed. It was found that the sex of the horses, the period spent daily in the paddock in the herd, the regularity of use and habituation to staying in isolation can all be classified as factors that have no effect on the heart rate, respiratory rate or behaviour during short-term isolation. It was suggested that the resting respiratory rate and the effect of isolation could be classified as features that are potentially useful in assessing horses’ adaptability to short-term social isolation.

Tryptophan (Trp) is an essential amino acid which metabolises via the kynurenine pathway to generate a number of bioactive substances referred to as kynurenines. Among those are 3-hydroxykynurenine (3-HKyn) and quinolinic acid, which are neurotoxic, as well as kynurenic acid (Kyna) and xanthurenic acid (XA), which, similarly to nicotinamide (NAm), show neuroprotective and anti-depressive effects. Routine exercise is known to modulate Trp metabolism in skeletal muscle and is thus believed to reduce the risk of depressive states in humans and laboratory animals. Analogously, it was hypothesised that exercise can influence Trp metabolism in horses as well. The aim of this study was to evaluate the influence of two different types of exercise on Trp metabolism in horses of the same breed. A total of 32 purebred Arabian horses were involved in the study. The 22 three-year-old racehorses were subjected to short-time intense exercise. Ten other horses were made to perform endurance competitions at a distance of 80 km. Blood samples were collected at rest and following the end of the exercise period. Plasma concentrations of Trp, kynurenine (Kyn), Kyna, 3-HKyn, XA and NAm were determined using Ultra-High Performance Liquid Chromatography-Electrospray Ionisation-Tandem Mass Spectrometry. Short-time intense exercise led to an increase in plasma concentrations of Kyn, Kyna and XA. The endurance effort induced an increase in Kyna and a decrease in Trp and NAm levels. Both types of exercise, short-time intensive exercise and endurance exercise induced an increase in Trp metabolites, especially Kyna, and did not induce an increase in Trp level. Thus, from a pathophysiological perspective of the kynurenine pathway’s influence on mental state, both types of exercise induced beneficial effects in horses.

Simple Summary Horses lacking exposure to cattle often show a fearful response when confronted with cows. In controlled conditions, we tested the responses towards two cows and a novel moving object in twenty horses in arena and hand-leading tests. The horses avoided the proximity of all stimuli, but of one of the cows the most. However, both cows provoked a stronger cardiac response than an inanimate object. We hypothesise that this response may be due to both neophobia and heterospecific interactions. Abstract Ridden horses have been reported to be fearful of cows. We tested whether cows could provoke behavioural and cardiac fear responses in horses, and whether these responses differ in magnitude to those shown to other potential dangers. Twenty horses were exposed to cow, a mobile object or no object. The time spent at different distances from the stimulus was measured. In a separate test, heart rate (HR), root mean square of successive differences between heartbeats (RMSSD) and the horses’ perceived fear were assessed at various distances from the stimuli. The horses avoided the area nearest to all stimuli. During hand-leading, the cow elicited the highest HR and lowest RMSSD. Led horses’ responses to the cow and box were rated as more fearful as the distance to the stimulus decreased. Mares had a higher HR than geldings across all tests. HR positively correlated with the fearfulness rating at the furthest distance from the cow and box, and RMSSD negatively correlated with this rating in cow and control conditions. Our results show that these horses’ avoidance response to cows was similar or higher to that shown towards a novel moving object, demonstrating that potentially, both neophobia and heterospecific communication play a role in this reaction.

Physical effort is one of the key aspects of keeping horses in good condition. The condition of the animal is reflected by multiple blood parameters. The newly discovered cytokine-apelin can pose one of them, however, so far, has not been studied in the horse population. Apelin is produced by adipocytes and myocytes and plays an important role in the energy metabolism of the body through the influence, for example, on the process of adipogenesis and lipolysis. The aim of this study was to investigate if physical effort of various intensity affects the plasma concentration of apelin in horses. The study involved 20 purebred Arabian horses divided into two groups. The first group included 10 race horses, aged 3 years, and second group included 10 horses aged from 6 to 12 years, used in endurance rides. Blood samples were collected from each horse at rest and after exercise. The concentrations of apelin, lactic acid, cortisol, uric acid (UA), triacylglycerols, total plasma protein, and glucose were determined in plasma samples. Race training sessions induced significant decreases in plasma apelin concentrations (P.05). In endurance horses, significant correlations were found only between exercise-induced changes of apelin and cortisol (r = 0.55) and apelin and UA (r = 0.67) concentrations. In conclusion, the concentration of apelin in equine plasma decreases in response to short-time exercise unlike endurance exercise. Blood plasma apelin concentration determined at rest is lower in long-time regularly trained horses than in the ones at the beginning of their training process.

The first aim of study was to assess the feelings of friendship and companionship among mares released into a paddock in different combinations by analysing the duration of behaviours occurring there as well as changes in heart rhythm. The second aim of the study was to develop a procedure for creating different herd configurations based on the individual affiliative needs of horses, expressed as a score. The study was conducted on 12 one-year-old Thoroughbred mares. It was carried out on three consecutive days during the horses’ 30-minute stay in the paddock. On the first day, all mares were in the paddock together. On the second day, they were released in pairs, and on the third day, they were released individually. Expressions of affiliative behaviours (feelings of friendship and companionship) towards another horse were timed. The activity of the parasympathetic system was measured as well. The results were used to score the mares’ affiliative behaviour using a procedure of our own design. Feelings of friendship and companionship were found to be most strongly expressed when a herd of horses with an established hierarchy including each individual was present on the paddock. Releasing horses in pairs is a good substitute for releasing the entire herd, but cannot replace true herd relations, due to decreased expression of feelings of closeness and companionship, such as play or grooming. Releasing horses into the paddock individually is not recommended because it disturbs social behaviour, thus increasing emotional excitability. Emotional excitability is calmed when horses are released in pairs, so this configuration can be used for excitable horses. The best solution, however, seems to be the use of the affiliative behaviour score proposed in the study, as an indicator of the individual needs of mares when creating various herd configurations.

The aim of the study was to assess the effects of training on haematological and biochemical blood parameters as well as on the changes in body surface temperature in horses. In order to identify the predictive value of surface temperature measurements as a marker of animal's performance, their correlations with blood parameters were investigated. The study was carried out on nine horses divided into two groups: routinely ridden and never ridden. Infrared thermography was used to assess surface temperature changes before (BT) and just after training (JAT) on a treadmill. Seven regions of interest (ROIs) located on the neck, shoulder, elbow, back, chest, gluteus and quarter were analysed. The blood samples were taken BT, JAT and 30 min after training (30AT). Haematological parameters including white blood cells, lymphocytes (LYMs), monocytes (MONOs), granulocytes (GRAs), eosinophils (EOSs), haematocrit (HCT) and platelets (PLTs) as well as biochemical parameters such as glucose (GLUC), urea, Na+, K+ and Ca2+, and creatine phosphokinase (CPK) were analysed. Our results indicated a significant increase in surface temperature JAT (p=0.043) in the neck, shoulder, elbow, gluteus and quarter in routinely ridden horses. Significant changes in EOS (p=0.046) and HCT (p=0.043) in the case of the never-ridden and routinely ridden group, respectively, were found between the times of blood collection. In addition, there was a significant effect of the horse group and the time of blood collection on the CPK activity (p=0.025 to p=0.045) and urea concentrations (p=0.027 to p=0.045). In the routinely ridden horses, there were significant correlations between the changes in MONO (ρ=0.40), GRA (ρ=-0.40), PLT (ρ=-0.77), HCT (ρ=-0.36), GLUC (ρ=0.56) and urea (ρ=0.56) and the total ROI temperature changes. Moreover, significant correlations between the changes in MONO (ρ=-0.86), EOS (ρ=-0.65), GLUC (ρ=0.85), urea (ρ=0.85), Na+ (ρ=0.59) and K+ (ρ=-0.85) and the total ROI temperature changes were found in never-ridden horses. Different changes in body surface temperature and blood parameters in routinely ridden and never-ridden horses could be associated with different conditioning and performance. A significantly higher surface temperature in routinely ridden horses, as well as the dynamics of changes in HCT, CPK and urea after training indicate better performance of these horses. Significant correlations between MONO, GLUC, and urea and a total ROI surface temperature as well as a negative correlation between MONO and the total ROI temperature in never-ridden horses indicated poor performance.

This article presents an overview of the literature on aging in the context of human–horse similarities and describes the role of animal models in the study of human geriatrics. For any given comparative aging study, the choice of a specific animal species is based on the physiological and pathophysiological resemblance of the aging process in animals and humans. In horses, the physique of the body, the course of the aging process, and the spectrum of naturally occurring diseases are similar to those in humans. Although the horse is not a laboratory animal, aging horses are a relatively numerous, which allows for geriatric studies on diseases with a similar course as in humans, for example, diabetes or polysaccharide storage myopathy. The potential benefits are two-pronged as some of the developments in human medicine can also be implemented in equine therapy. Moreover, aged horses can be used in hippotherapy for elderly people. In the near future, horses may be able to help extend the human lifespan or at least diminish the consequences of aging.

The aim of this study was to determine the influence of different forms of an audience's behavior on the heart work parameters and salivary cortisol level of leisure horses during work. Twelve horses were studied at rest, during standardized work, and at recovery. There was no audience in the arena in the control variant, whereas an audience (10 people) was situated in the middle of the arena in four other variants: standing still and silent in the first variant, standing still and talking in normal voice in the second variant, being silent but walking in both directions along the middle line of the arena in the third variant, and walking as above and simultaneously talking in the fourth variant. Heart rate, heart rate variability parameters: root mean square of successive beat-to-beat differences, low frequency of the power spectrum (LF), high frequency of the power spectrum (HF) and ratio of LF and HF signal (LF/HF), as well as salivary cortisol levels were measured. We found that audience presence and various forms of behavior during horse-riding leisure hours caused a significant decrease (P

Background Predatory attacks on horses can become a problem in some parts of the world, particularly when considering the recovering gray wolf populations. The issue studied was whether horses transformed by humans and placed in stable-pasture environments had retained their natural abilities to respond to predation risk. The objective of the study was to determine the changes in cardiac activity, cortisol concentrations, and behavior of horses in response to the vocalizations of two predators: the gray wolf (Canis lupus), which the horses of the breed studied had coevolved with but not been exposed to recently, and Arabian leopard (Panthera pardus nimr), from which the horses had been mostly isolated. In addition, we hypothesized that a higher proportion of Thoroughbred (TB) horse ancestry in the pedigree would result in higher emotional excitability in response to predator vocalizations. Nineteen horses were divided into groups of 75%, 50% and 25% TB ancestry. The auditory test conducted in a paddock comprised a 10-min prestimulus period, a 5-min stimulus period when one of the predators was heard, and a 10-min poststimulus period without any experimental stimuli. Results The increase in heart rate and saliva cortisol concentration in response to predator vocalizations indicated some level of stress in the horses. The lowered beat-to-beat intervals revealed a decrease in parasympathetic nervous system activity. The behavioral responses were less distinct than the physiological changes. The responses were more pronounced with leopard vocalizations than wolf vocalizations. Conclusions The horses responded with weak signs of anxiety when exposed to predator vocalizations. A tendency towards a stronger internal reaction to predators in horses with a higher proportion of TB genes suggested that the response intensity was partly innate. The more pronounced response to leopard than wolf may indicate that horses are more frightened of a threatening sound from an unknown predator than one known by their ancestors. The differing response can be also due to differences in the characteristic of the predators’ vocalizations. Our findings suggested that the present-day horses’ abilities to coexist with predators are weak. Hence, humans should protect horses against predation, especially when introducing them into seminatural locations.

The aim of this study was to determine the taste preferences of horses in relation to their breed and sex. Forty-eight adult purebred Arabian, Anglo-Arabian, Polish Konik, and Polish cold-blooded horses—stallions and mares in equal numbers—were examined in the study. During the experiment, five types of industrially processed feeds based on oats and natural dried products commonly regarded as horse treats (i.e., sour and sweet apples, carrots, sugar beet molasses, and barley with salt) were given to horses in buckets on three consecutive days. The behavior of the horses during the experiment was evaluated, as was the way in which they expressed their taste preferences, the sequence in which they consumed the pellets, the time they took to become interested in the pellets, and the time they took to consume each kind of pellet. The taste preferences of the horses were found to depend on their breed and sex. Pellets containing molasses were consumed more willingly by mares than stallions. Feeds with the addition of apples or carrots were the favorite treats of all tested breeds. The greatest variety in pellet taste preferences was found in purebred Arabian horses. Pellets with a distinct sweet taste or slightly salty cereals should be given to horses if other options are not available. In most cases, these two additions were chosen last by the horses in the experiment. Primitive horses had a distinct manner of expressing taste sensations. Horse behavior indicating an interest in a feed should not be taken as a proof of its tastiness. The first food chosen is not necessarily the one consumed most quickly.

Relaxing massages and playing music in stables may be used to mitigate the high level of stress in race horses. In the study, we compared effects of different frequencies of massages and different hours of music for race horses. Sixty horses were equally divided into one control group and four experimental groups. The experimental groups were treated with various relaxing methods: music for 1 hour a day, music for 3 hours a day, massage on the day preceding a race, and daily massage during the 6 months of the racing season. To evaluate the effects of the methods, horses' heart rate (HR) and parameters of heart rate variability (ratio of low to high frequencies of the power spectrum–LF/HF, and root mean square of successive beat-to-beat difference [RMSSD]) were measured while preparing horses for training sessions. Salivary cortisol concentrations were measured before and after training sessions. Official general handicap and success coefficient in the racing season were considered as performance parameters. In the experimental groups, lowered HR, LF/HF, and salivary cortisol concentrations as well as increased RMSSD were found, however, at various levels. The most positive changes in the parameters under study were found in horses massaged every day, which shows that relaxing massages are beneficial for horses' welfare and performance. Massages only about once every 3 weeks also gave some positive effects. It was shown that playing relaxing music for 3 hours a day had more positive effects on horses' emotional state than for 1 hour.

Horses intended for leisure riding do not undergo any selection and most often retired sports horses or defective horses are chosen, as a low selling price determines their purchase by a leisure riding center. Unfortunately, horses bought at low prices usually have low utility value, are difficult to handle, require a special or individual approach and do not provide satisfaction in riding. However, neither modern horse breeding nor scientific research address the need to breed horses for leisure activities. There is no clear definition of a model leisure horse and criteria or information for its selection are not readily available in scientific publications. A wide spectrum of research methods may be used to evaluate various performance traits in horses intended for leisure activities. The fact that the population of recreational horses and their riders outnumber sporting horses should attract the special attention of scientific research. Their utility traits need to be determined with modern technology and methods in the same way they are for sporting horses. Such a system of evaluation would be very helpful for riders.

The current predation threat of domestic horses is generally low, and horses do not know predators' frightening cues. We studied whether horses still recognise predation threats. The aim of the study was to analyse the emotional response of purebred Arabian horses (Arabian) and Polish Konik horses (Konik) to an Arabian panther (Panthera pardus nimr) (panther) growl and a grey wolf (Canis lupus) (wolf) howl. Panther vocalisation was known to Arabian ancestors, whereas ancestors of Konik knew wolf vocalisation. The response to the howls of golden jackals (Canis aureus) (jackal), which did not prey on equids, was also studied comparatively. Two groups of 10 adult horses of each breed were subject to predator sounds of one predator daily for 5 min during a turn out on pasture. The test was performed for 18 days in total. The sound of each predator was interchangeably featured from one loudspeaker for 3 days followed by four loudspeakers simultaneously to imitate a group of predators for 3 days. The horses' emotional agitation in response to the sounds was measured based on the parameters of heart rate variability (HRV) using telemetric devices. The results showed that the predators' sounds were identified by horses as stressful or neutral. Horses generally retained their anti-predator responses even in the current habitat, which typically lacks predation cues. The results are not always coherent and may demonstrate that the response is somewhat attenuated. The wolf howl elicited a stronger response in Koniks. The panther growl more strongly influenced Arabians, whereas the jackal howl minimally elicited an agitation in the horses. The differentiated response of the two horse breeds to the three predator species suggests that the response is an innate adaptation to the predation risk in the habitat of the breed ancestors. This response occurs regardless of the emotional arousal specific to a breed, and the frightening cue is not the sound per se but the possible attack of predators. Horses display a type of understanding of the sound meaning. Their HRV response seems to be adequate for the threat signalised by the sound.

The aim of the study was to investigate the feasibility of evaluating heat loss from the body surface of horses during exercise on a treadmill using dynamic infrared thermography (IRT). Continuous measurements of body surface temperature change at walk, trot, and during recovery time were collected from five horses using a thermographic camera. Horses were exercised on the treadmill for 25 minutes: 10 minutes of walk, 10 minutes of trot, 5 minutes of walk, and ending with 10 minutes of recovery time. Four thermograms per minute were extracted from the original 30 Hz video sequences for temperature analysis. Four regions of interest (ROIs) were positioned on each analyzed thermographic image including neck (NC), shoulder (SH), chest (CH), and croup area. At baseline, the NC was the hottest ROI, followed by the SH. By the end of the first walk, the temperature at all ROIs had increased, with the NC area remaining the warmest. During the trot, temperature increased for the first 5 minutes, with the greatest increase in temperature in the CH area. During the second walk, the temperatures started to decline in all regions. By the end of the recovery period, temperature had reduced at all regions, with the NC and CH areas demonstrating the biggest drop in temperature. It was found that heat loss from the body surface during exercise can be evaluated by means of dynamic body surface temperature measurement with IRT. More research is now required to fully explore the physiological changes of the equine musculoskeletal system during exercise.

In humans and animals, aging leads to a decrease in immune function and an increased susceptibility to infection. Decreased immunity and an increase in the incidence of infectious diseases are particularly notable during the autumn. Bee pollen supplementation improves immunity and antioxidant enzyme activity, as well as general performance. The aim of this study was to evaluate the effects of bee pollen supplementation during the autumn on blood parameters in aged horses. The study was performed on 16 warmblood horses aged 15–26 years. Half of this group received 60 g of bee pollen (soaked in water) daily for 30 days during the autumn season. Blood samples were taken from all horses before and after the supplementation period. Numerous hematological and plasma biochemical parameters including indicators of oxidative stress were determined. The data collected after the supplementation were compared with data collected before the experiment using one-way analysis of variance and paired Student’s t-test. In the control group, there was a decline in the total number of red blood cells, hemoglobin, and hematocrit and an increase in some lipid parameters, urea, total plasma proteins, and sulfhydryl groups. Supplementation with bee pollen prevented the variation of these parameters, except for low-density lipoprotein cholesterol. We believe that bee pollen supplementation for aged horses during autumn has beneficial effects because it inhibited some of the adverse changes observed in the control horses during this season.

It was assumed that a horse with its rider body weight found in the upper limit may negatively impact the horse&rsquo, s welfare. The objective of this paper was to analyze the differences in body temperature and selected heart rate parameters in horses in response to physical exercise accompanied by various rider&rsquo, s body weight loads. The study was carried out on 12 leisure, 10&ndash, 15-year-old warmblood geldings. The horses were ridden by two equally qualified riders whose body weights were about 20% and 10% of the average body weight (BW) of the animals (about 470 kg). Each rider rode each of the 12 horses for 13 min walking and 20 min of trotting. Images of the horse at rest, after physical exercise directly after unsaddling, and during the recovery phase (10 min after unsaddling) were taken with an infrared thermography camera. For analysis, the temperatures of selected body parts were measured on the surface of the head, neck, front, middle, and back (croup) parts of the trunk, forelimb, and hind limb. Immediately after the infrared thermography images were taken, the rectal temperature of the horse was measured. The heart rate parameters were measured at rest for 10 min directly before, during, and 10 min following the end of a training session. A multivariate analysis of variance (ANOVA) for repeated measurements was performed. Statistical significance was accepted for p &lt, 0.05. A rider BW load on a horse of approximately 20% of the horse&rsquo, s BW led to a substantial increase in the superficial temperatures of the neck, front, middle, and back parts of the trunk in relation to these body parts&rsquo, average temperatures when the load was about 10% BW. The head and limb average temperatures were not significantly affected by the load of the exercised horse. A horse&rsquo, s load above 20% of his body weight, even with little effort, affects changes in surface temperature and the activity of the autonomic nervous system.

Development of the musculoskeletal system occurs, in part, through an impact on regulatory proteins, such as activin A and decorin. Activin A induces atrophic effects on skeletal muscle, and decorin regulates the formation of connective tissue proteins like collagen and elastin in tendons and ligaments. The aim of this study was to evaluate the influence of different intensities of exercise on blood plasma activin A and decorin concentrations in horses. Ten young purebred Arabian horses were subjected to routine training sessions on a racetrack, and another 11 adult horses of the same breed participated in endurance rides. Race horses were examined during gallop tests over a distance of 1200 m and endurance horses at distances from 20 to 80 km. Blood samples were collected at rest and after exercise to determine plasma concentrations of activin A, decorin and cortisol. Despite differences in the intensity of exercise, the plasma decorin concentration remained unchanged, and activin A tended to decrease in endurance horses only. The exercise-induced changes in plasma activin A concentrations correlated with the covered distance (r = -0.43; P.05), but not with the changes in cortisol values. Further studies are needed to confirm the usefulness of plasma activin A as a potential indicator of a horse's endurance performance.