Horses In Training Research Articles

Comparing lying behaviour of young riding horses on days in an individual indoor box, on an outdoor paddock alone, or in pairs and in the following night.

Horses must lie down to go into vital rapid-eye movement (REM) sleep. If they are not lying down for sufficiently long periods they can become so sleep-deprived that they collapse uncontrollably, which results in a risk of injuries. To investigate how recumbency as a prerequisite to REM sleep on the experimental days and the following nights was influenced by changes in social and spatial environment throughout the day. Cross-over design in which subjects experienced each experimental condition twice. Observations were conducted on a horse farm. Ten young horses in training were observed on days when they were alone indoors in a box, on an outdoor paddock alone, on the same paddock in pairs, and in the following night stabled alone. The number of lying bouts and the total lying duration throughout the day and night were assessed automatically using 3D-accelerometers and data were evaluated using mixed-models. Horses had a higher number of lying bouts during the days (p = 0.05, by a factor of 1.21 [95% CI: 1.00-1.45]) and longer lying duration at night (p < 0.001, by a factor of 11.25 [6.47-18.40]). On average, the number of lying bouts and the duration of lying increased from being indoors alone, to being outdoors alone, and outdoors in pairs although this could not be statistically supported (bouts: p = 0.5, by a factor of 1.08 [0.84-1.36] and 1.17 [0.91-1.48]; p = 0.6, duration: by a factor of 1.39 [0.73-2.93] and 1.38 [0.68-2.78]). A small number of horses were observed and there was large variability between days within horses. We found some indications that open space and a social companion throughout the day increased time lying down in the day as well as during the following nights thus allowing for more REM sleep.

Effect of circle, surface type and stride duration on vertical head and pelvis movement in riding horses with pre-existing movement asymmetries in trot.

Head and pelvis vertical movement asymmetries in horses are often evaluated under different conditions yet better understanding is required of how these asymmetries are altered by factors such as surface type or circle size. This study investigated how stride duration, surface and lungeing in circles of different sizes influenced objectively measured head and pelvis movement asymmetries in riding horses in full training. Movement asymmetries were recorded with body mounted accelerometers and were based on the differences between the two vertical displacement minima or maxima of head (HDmin, HDmax) and pelvis (PDmin, PDmax) within a stride cycle. Each horse was evaluated during straight-line trot and during lungeing (d = 10m/15m) on hard and soft surfaces at slow and fast speed (determined by stride duration). All horses (N = 76) had at least one movement asymmetry parameter above a predefined thresholds (|HDmin| or |HDmax| >6mm, |PDmin| or |PDmax| >3mm) during a straight line trot on hard surface (baseline). The horses were assigned to a 'predominant asymmetry' group (HDmin, HDmax, PDmin, PDmax) based on which movement asymmetry parameter was the greatest during the baseline condition; the head movement asymmetry values were divided by two to account for the difference in magnitude of the thresholds. Analysis was carried out for each predominant asymmetry group separately using linear mixed models-outcome variable: predominant asymmetry parameter; random factor: horse; fixed factors: surface, direction with stride duration as covariate (P<0.05, Bonferroni post-hoc correction). The 'direction' conditions were either a straight-line locomotion ('straight') or lungeing with lungeing conditions further classified by circle diameter and by whether the limb which the predominant asymmetry was assigned to ('assigned limb') was on the inside or outside of the circle ('inside10', 'inside15', 'outside10', 'outside15'). Only parameters related to asymmetrical weight-bearing between contralateral limbs (HDmin, PDmin) were affected by changes in stride duration-the most common pattern was an increase in asymmetries as stride duration decreased. Only pelvic movement asymmetries were affected by lungeing. When the assigned hindlimb was on the inside of the circle, the PDmin asymmetries increased and PDmax asymmetries decreased compared to the straight-line condition. With the assigned hindlimb on the outside, PDmin asymmetries decreased but PDmax asymmetries did not change. Trotting on 10 m circle compared to 15 m circle did not increase movement asymmetries. In conclusion, circular motion and changes in stride duration altered movement asymmetries identified in horses in full ridden work but no changes were seen between the soft and hard surfaces. These patterns should be further investigated in clinically lame horses.

Can equine communication via audible exhales improve the welfare of therapy horses? – A pilot practice project

Abstract Background: Human-animal interactions in human services are on the rise, with an increased focus on the welfare of animals involved as well as on client safety. Based on scientifically based training methods, it has been proposed that horses involved in therapy settings could benefit from learning proactive strategies to reduce stress. One possible strategy is audible exhale communication (AEC). Inviting horses to actively use this strategy with humans could enhance the welfare of horses in equine-assisted therapy (EAT), thereby increasing client safety. Methods: A pilot project was conducted to test the feasibility of training 20 therapy horses to use AEC as a veto signal for an activity, while therapists responded to the signals. The number of audible exhales from the horses was compared between the initial and final training sessions. Furthermore, we tested whether age, years of training experience, and therapy experience served as moderating variables for the outcome. Additionally, qualitative observations were made by therapists working with the horses. Results: It has become apparent that training the horses to use AEC was successful. After 6 months of training, the horses showed a significantly higher number of audible exhales than in the initial training session, with a large effect size. Neither age nor years of training or therapy experience was found to be a moderating variable. The horses were eagerly engaged with newly acquired tools. These showed fewer indications of stress, greater sense of relaxation, and more positive emotions. Conclusion: Based on the findings of this pilot study, training horses to use AEC might be a feasible approach to reduce stress in horses working in therapeutic settings, increase client safety, enhance human-animal relationships, and open up new possibilities for improving the therapeutic process. This method is applicable to all horses, regardless of their age, training level, or experience in therapy. For future research, it would be interesting to replicate and extend the approach by addressing the aforementioned limitations and using a randomized controlled design to investigate the introduction and impact of AEC in a therapeutic setting and to gain more comprehensive insights.

Cardiovascular training adaptations in Criollo breed horses: biochemical markers and morphofunctional parameters

Abstract The aim of the present study was to investigate the cardiovascular morphofunctional and biochemical training adaptations of Criollo breed horses. Thirty-one animals were evaluated, arranged in two groups – untrained horses, used as a control group (n = 17); trained horses, in training for the Freio de Ouro competition (n = 14). The means and standard deviation of echocardiographic, electrocardiographic and biochemical variables were measured and, subsequently, compared between groups of trained and untrained animals using Student’s t test, considering . Trained horses had lower biochemical levels of CK, CKMB and cTnI I when compared to untrained animals. The echocardiographic variables interventricular septum during diastole (IVSd), left ventricular free wall during systole (LVFWs), left ventricular free wall during diastole (LVFWd), left ventricular mass (LVMass), diameter of the aorta (Ao) and diameter of the left atrium (LA) have shown higher values in trained horses compared to untrained. Duration of the T wave was the only electrocardiographic variable that was influenced by training, showing higher values for untrained animals. Therefore, there is influence of training on biochemical variables, in addition to on morphological and functional echocardiographic/electrocardiographic characters in trained Criollo breed horses, characterised by concentric cardiac hypertrophy, when compared to untrained individuals. In addition, a majority of normal sinus heart rhythm was observed in the animals evaluated.

Positron emission tomography assessment of metacarpal/metatarsal condylar fractures post surgical repair: Prospective study in 14 racehorses.

To assess 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) findings associated with metacarpal/metatarsal condylar fractures at the time of fracture repair and through healing. Prospective descriptive study. Fourteen Thoroughbred racehorses. 18F-NaF PET was performed within 4 days of surgical metacarpal/metatarsal condylar fracture repair, on both the injured and contralateral limb. Follow-up PET scans were offered at 3- and 5-months post fracture repair. Areas of abnormal uptake were assessed using a previously validated grading system. Eight fractures were located in the parasagittal groove (PSG) (six lateral and two medial) and six fractures were located abaxial to the PSG (non-PSG) through the palmar/plantar condyle (all lateral). All horses in the latter group had uptake in the lateral palmar condyle of the contralateral limb suggestive of stress remodeling. Three horses with PSG fractures had uptake in a similar location in the contralateral limb. Horses with lateral condylar fracture only presented minimal or mild uptake in the medial condyle, which is considered atypical in the front limbs for horses in full training. Four horses developed periarticular uptake in the postoperative period suggestive of degenerative joint disease, three of these horses had persistent uptake at the fracture site. These four horses did not return to racing successfully. The findings of this study provide evidence of pre-existing lesions and specific uptake patterns in racehorses suffering from metacarpal/metatarsal condylar fractures. PET has a possible role in the prevention, diagnosis, and postoperative monitoring of metacarpal/metatarsal condylar fractures in racehorses.

Effect of high-starch or high-fibre diets on the energy metabolism and physical performance of horses during an 8-week training period.

Large amounts of high-starch concentrates are traditionally fed to horses in training. However, this has been associated with digestive or muscle diseases and behavioural modifications. In parallel, it has been demonstrated that horses fed high-fibre, low-starch diets achieve the same performance over an exercise test as the ones fed high-starch diets. However, whether the same performance level can be maintained over a longer training cycle is still being determined. This study aimed to compare the evolution in physical performance and cardiorespiratory responses of two groups of French Trotters fed either a control high-starch (15.0g dry matter hay/kg body mass/day + 6.6g dry matter oats/kg body mass/day) or a high-fibre diet (75% of oats replaced by dehydrated alfalfa) over an 8-week training period. The horses that entered the trial were untrained for ≥4months and previously fed hay only. Track training with speed monitoring included interval training sessions and 2400m performance tests from week 1 to week 8 (W8). Before (week 0, W0) and after (week 9, W9) the training period, horses performed an incremental continuous exercise test during which cardiorespiratory parameters were measured. Both groups progressed to the same extent regarding physical performance measured during interval training sessions (acceleration: 0.16m.s-2 at W0 and 0.40m.s-2 at W8; p < 0.0001), the 2400m performance test (average speed: 8.88m.s-1 at W0 and 10.55m.s-1 at W8; p < 0.0001), and the incremental continuous exercise test (speed during the fastest stage: 9.57m.s-1 at W0 and 10.53m.s-1 at W9; p = 0.030). Although oxygen consumption increased with training (p = 0.071), it was not influenced by the diet. On the contrary, carbon dioxide production increased in the high-starch group only (high-starch group: 84.0 vs. high-fibre group: 77.7mL.kg-1.min-1 at W9; p = 0.031). The results illustrate that horses in both groups progressed similarly but did not use the same metabolic pathways during exercise. This hypothesis is supported by carbohydrate oxidation, which tended to increase in the high-starch group at W9 but decreased in the high-fibre group (p = 0.061). In conclusion, the substitution of high-starch by high-fibre diets enabled similar performance over an 8-week training period and altered energy metabolism in a way that could be beneficial during high-intensity exercise.

Naturalistic Elements in Percival Everett’s Wounded

This article examines Percival Everett’s 2005 novel Wounded through three applications of the word “naturalistic” in order to show how the work complicates divisions between nature and man and man and animal. First, the article shows how its protagonist, John Hunt, contends with his relationship to nature as both a source of respite and as part of his livelihood as a horse trainer. Next, “naturalistic” elements of Wounded reveal how the mythic West of classic Westerns has influenced perspectives on the “real” West. Finally, the article assesses Wounded as a work of American literary naturalism, particularly in terms of the questions it inspires about free will and determinism. Together, these applications of the word “naturalistic” expose how nature acts as John’s barometer for human morality and individualism, forcing us to question whether man is truly superior over nature.

Physiological Adaptation To High-Intensity Interval Training And Moderate-Intensity Continuous Training In Horses

Physiological Adaptation To High-Intensity Interval Training And Moderate-Intensity Continuous Training In Horses

Acute exercise in a hot environment increases heat shock protein 70 and peroxisome proliferator-activated receptor γ coactivator 1α mRNA in Thoroughbred horse skeletal muscle.

Heat acclimatization or acclimation training in horses is practiced to reduce physiological strain and improve exercise performance in the heat, which can involve metabolic improvement in skeletal muscle. However, there is limited information concerning the acute signaling responses of equine skeletal muscle after exercise in a hot environment. The purpose of this study was to investigate the hypothesis that exercise in hot conditions induces greater changes in heat shock proteins and mitochondrial-related signaling in equine skeletal muscle compared with exercise in cool conditions. Fifteen trained Thoroughbred horses [4.6 ± 0.4 (mean ± SE) years old; 503 ± 14 kg] were assigned to perform a treadmill exercise test in cool conditions [COOL; Wet Bulb Globe Temperature (WBGT), 12.5°C; n = 8] or hot conditions (HOT; WBGT, 29.5°C; n = 7) consisting of walking at 1.7 m/s for 1 min, trotting at 4 m/s for 5 min, and cantering at 7 m/s for 2 min and at 90% of VO2max for 2 min, followed by walking at 1.7 m/s for 20 min. Heart rate during exercise and plasma lactate concentration immediately after exercise were measured. Biopsy samples were obtained from the middle gluteal muscle before and at 4 h after exercise, and relative quantitative analysis of mRNA expression using real-time RT-PCR was performed. Data were analyzed with using mixed models. There were no significant differences between the two groups in peak heart rate (COOL, 213 ± 3 bpm; HOT, 214 ± 4 bpm; p = 0.782) and plasma lactate concentration (COOL, 13.1 ± 1.4 mmoL/L; HOT, 17.5 ± 1.7 mmoL/L; p = 0.060), while HSP-70 (COOL, 1.9-fold, p = 0.207; HOT, 2.4-fold, p = 0.045), PGC-1α (COOL, 3.8-fold, p = 0.424; HOT, 8.4-fold, p = 0.010), HIF-1α (COOL, 1.6-fold, p = 0.315; HOT, 2.2-fold, p = 0.018) and PDK4 (COOL, 7.6-fold, p = 0.412; HOT, 14.1-fold, p = 0.047) mRNA increased significantly only in HOT at 4 h after exercise. These data indicate that acute exercise in a hot environment facilitates protective response to heat stress (HSP-70), mitochondrial biogenesis (PGC-1α and HIF-1α) and fatty acid oxidation (PDK4).

Dynamics of training and acute exercise-induced shifts in muscular glucose transporter (GLUT) 4, 8, and 12 expression in locomotion versus posture muscles in healthy horses.

Important changes in glucose transporter (GLUT) expression should be expected if the glucose influx plays a pivotal role in fuelling or connecting metabolic pathways that are upregulated in response to exercise. The aim was to assess GLUT4, 8, and 12 dynamics in response to training and acute exercise. Methods: Sixteen untrained Standardbred mares (3-4year) performed an incremental SET at the start and end of 8weeks harness training. M. pectoralis (PM) and M. vastus lateralis (VL) muscle biopsies were taken before and after each SET, allowing for comparing rest and acute samples in untrained (UT) and trained (T) condition using Western Blot for GLUT quantification and Image Pro v.10 for Blot analysis. Data were normalized against GAPDH. Basal GLUT-levels of PM versus VL were analysed with the Wilcoxon matched-pairs signed rank test. The effect of acute exercise or training was assessed using the Friedman test with a post hoc Dunn's. Results: Basal GLUT4 and GLUT12 protein expression were significantly higher in the VL compared to the PM (PGLUT4 = 0.031 and PGLUT12 = 0.002). Training had no effect on basal GLUT4 expression, neither in the VL (p > 0.9999), nor the PM (p > 0.9999). However, acute exercise in trained condition significantly decreased GLUT4 expression in the VL (p = 0.0148). Neither training nor acute exercise significantly changed total GLUT8 protein expression. Training significantly decreased total GLUT12 protein expression in rest biopsies, only visible in the VL (p = 0.0359). This decrease was even more prominent in the VL after acute exercise in trained condition (PVL = 0.0025). Conclusion: The important changes seen in GLUT12 expression downregulation, both in response to training and acute exercise in the horse, the downregulation of GLUT4 expression after acute exercise in trained condition and the lack of differential shifts in GLUT8 expression in any of the studied conditions, questions the importance of glucose as substrate to fuel training and exercise in healthy horses. These findings encourage to further explore alternative fuels for their involvement in equine muscular energetics.

Does social motivation mitigate fear caused by a sudden sound in horses?

Living in a herd has multiple advantages for social species and is a primary survival strategy for prey. The presence of conspecifics, identified as a social buffer, may mitigate the individual stress response. Social isolation is, therefore, particularly stressful for horses, which are gregarious animals. However, they are not equally vulnerable to separation from the group. We tested whether more and less socially dependent horses and independent individuals would differ in their responses to novel and sudden sounds occurring in two contexts: non-social and social motivation. Twenty warmblood horses were first exposed to two social tests: to evaluate the level of social dependence (rate of restless behaviour; social isolation) and the quantity and the quality of interactions in which they were involved (stay on a paddock). Two fear audio tests were then performed to compare the responses to sudden sounds while feeding (non-social motivation; control trial) and while moving towards the herd (social motivation; experimental trial). Socially dependent horses showed more pronounced avoidance behaviour and needed much more time to resume feeding during the control trial. Hence, dependent individuals appeared to be more fearful. However, during an experimental trial, horses of both groups tended to ignore the sound or paid only limited attention to the stimulus, continuing to move forward towards their conspecifics. Thus, social motivation may mitigate fear caused by a frightening stimulus and make fearful and dependent horses more prone to face a potentially stressful event. This finding should be taken into account in horse training and management.

Long-term monitoring of clodronate in equine hair using liquid chromatography-tandem mass spectrometry

Given the potential for long-term inhibition of bone remodeling/healing and detrimental effects to horses in training, bisphosphonates are tightly regulated in horseracing. Hair has proven to be an effective matrix for detection of drug administration to horses and has been particularly effective in detecting drugs for a long period of time post administration. Thus, hair may prove to be a useful matrix for detection of administration of this class of drugs. The objective of the current study was to develop an assay and assess the usefulness of hair as a matrix for long-term detection of clodronate to horses. Seven horses received a single intramuscular administration of 1.8 mg/kg clodronate. Hair samples were collected prior to and up to 6 months post administration. A liquid chromatography-tandem mass spectrometry method was developed and concentrations of clodronate measured in hair samples. The drug was first detected on day 7 in 4/7 horses, and on days 14, 28 and 35 in the remaining three horses. In 4/7 horses, clodronate was still detectable 6 months post administration. Results of this study demonstrate that, although there was significant inter-individual variability in detection times (63 to 180 days) and several intermediate times where the drug could not be detected but was subsequently detected in later timepoints, clodronate administration was detectable in hair for a prolonged period in most of the horses (4/7) studied.

The charioteering in the Bronze Age societies of the Southern Trans-Urals as a social phenomenon

The sites of the Sintashta and Petrovka archaeological cultures of the Bronze Age of the Southern Trans-Urals (Russia) have been traditionally considered as part of the realm of chariot cultures of early Indo-European communities. The analysis of the finds demonstrates that the phenomenon of charioteering carried an important symbolic role in the paradigm of the steppe communities of the Bronze Age. Numerous finds of chariot fragments, elk antler cheekpieces, paired horse sacrifices, remote combat weapons in cemeteries of Stepnoye I, Stepnoye VII, and Krivoe Ozero have been repeatedly subjected to scientific investigation. Collective burials have been discov-ered, in which even women and young children are accompanied by weapons, cheekpieces, fragments of chari-ots and sacrificial horses. Based on this, we have concluded that the community of “charioteers” included mem-bers of a certain clan, possibly related to the production and use of chariots, horse training, etc. At the same time, however, individual burials of adult men with elements of a chariot complex have also been found, which occupied central positions in kurgans; those men could have been actual chariot warriors. Recent findings provide a vivid evidence for this. In the field season of 2021, the Sintashta burial complex (kurgan 33) was investigated in the Stepnoye I cemetery, the central burial of which contained a skeleton of a 35–50 year old man who had a round healed hole in his skull. Theoretically, such an injury could have been caused by a battle axe, similar to ones found at the sites of the Sintashta and Petrovka Cultures. Furthermore, abnormal osteophytosis growths have been recorded on all areas of the man's spine, which could have resulted from both injury and high pressure on spine caused by driving a chariot. One elk antler cheekpiece (an element of horse bridle) was found in the burial, along with numerous bones of sacrificial animals. All details of the burial rite indicate that the buried man was a sig-nificant person for the community, probably a charioteer warrior. Previously obtained AMS dates attribute the Sin-tashta complexes of the Stepnoye I cemetery to the range of about 1950–1850 BC. Thus, the newly investigated kurgan 33 of the Stepnoye I cemetery respresents another piece of evidence indicating the existence of chariot cul-ture among the steppe communities of the Bronze Age in the Southern Trans-Urals.

A review of current chemistry, pharmacology, and regulation of endogenous anabolic steroids testosterone, boldenone, and nandrolone in horses.

Anabolic androgenic steroids are synthetic substances related to the male sex hormones (androgens). These agents promote the growth of skeletal muscle (anabolic effects) and the development of male sexual characteristics (androgenic effects). Anabolic steroids have been illegally used for many years as performance-enhancing drugs in human, equine, and canine sports and as growth promoters in livestock reared to provide meat for human consumption. The analytical challenge to developing effective means of control within these fields has been exacerbated by the reported endogenous nature of some of these steroids. Anabolic steroids have been employed extensively in equine practice over the past 50 years. Their usefulness is largely dependent on subjective opinions, as only minimal studies investigating pharmacodynamics have been carried out in horses. Therefore, their use will vary markedly between practitioners depending on their personal experiences and pressures by trainers to use them. They form part of rational therapy in a variety of conditions. In addition to their use for increasing muscle mass, they are used to varying extents in the raising of yearlings and in the training and racing of horses with the view of improving performance. The use of these agents is prohibited in the horseracing industry by the Association of Racing Commissioners International (ARCI), International Federation of Horseracing Authorities (IFHA), and Fédération Equestre Internationale (FEI).

Serum C-reactive Protein and Protein Electrophoretic Pattern Correlated With Age in Horses

Inflammaging or chronic, low-grade inflammation is a phenomenon characterizing age-related pathologies and natural processes in aging tissues. This study aimed to investigate the effect of age on the serum levels of C-reactive protein and protein electrophoretic pattern in horses. Thirty Italian Saddle horses from the same horse training center, were enrolled and divided in three equal groups according to their age: Group A (2-4 years), Group B (7-10 years), Group C (15-20 years). Blood samples were collected from each horse to evaluate hematological parameters and the serum concentration of C-reactive protein (CRP), total proteins, albumin, α1-, α-2, β1-, β2- and γ-globulins. One-way analysis of variance showed an age-related difference in the concentration of CRP, α1- and α2-globulins (P < 0.001) which increased with aging. Albumin and albumin:globulin ratio showed lower values in Groups B and C than Group A (P < 0.001). Age of horses showed a negative correlation with the values of albumin, and a positive correlation with CRP, α1- and α2-globulins concentration. The results of the current study suggest an increased acute phase response in adult and old horses compared to young ones. As α-globulin fractions include many other acute phase proteins (APPs) in addition to CRP, further studies to assess what other APPs could be involved in chronic inflammation or “inflammaging” are recommended in horse in order to improve knowledge on the key inflammatory biomarkers during aging in this species.

Back motion in unridden horses in walk, trot and canter on a circle

Equine back function is of concern to riders, as well as to veterinarians and physiotherapists; these groups may benefit from knowledge about spinal motion on the circle. This descriptive and comparative study aimed to quantify equine neck, back and pelvic motion in walk, trot and canter on a 9 m circle. Sixteen healthy horses in training, of varying breed and conformation, were measured using optical motion capture (150 Hz), with optical markers on the poll, withers, T15, tubera coxae and lumbosacral joint. Cervicothoracic and thoracolumbar flexion–extension and lateral bending, and pelvic roll, pitch and yaw, were statistically evaluated using mixed models. Motion patterns showed distinct differences between gaits, but were generally similar between horses. The thoracolumbar back was bent towards the inside of the circle (stride mean 5-6º for all gaits). The cervicothoracic spine was more flexed in walk (18°), and more extended in canter (-4—-8°), compared to trot (6–7°), whereas the thoracolumbar spine was slightly less extended in canter than in walk. Thoracolumbar flexion–extension range of motion (ROM) increased from walk (4°) to canter (9°), as did pelvic pitch ROM (walk 7° and canter 15–16°), while back lateral bending ROM and pelvic yaw ROM were lowest in trot. Taken together, the study findings suggest that neck and back motion patterns on the circle reflect an interaction between the constraints of circular movement, and the mechanics and characteristics of each gait.

45 Quantifying gait quality changes in fragile foal syndrome carriers using artificial intelligence

The domestic horse has remarkable locomotor polymorphisms valuable to study of genetic musculoskeletal diseases and their effect on gait quality. Here we investigate a polymorphism in the PLOD1 gene, responsible for Fragile Foal Syndrome (FFS), as it impacts the organization of collagen fibers. We hypothesize that the changes in the biomechanical properties of tissues will result in change of locomotor phenotypes. We first addressed the need for a gait assessment tool that can accurately quantify various locomotor parameters. We created a pipeline built around the software package DeepLabCut (DLC), a user-friendly graphical user interface (GUI) written in Python, and a custom gait parameter calculator written in MatLab. DLC uses a pre-trained deep neural network model to apply 22 anatomical landmarks on jogging horses observed in video recordings. A custom GUI allows the user to perform error checks of the labels before the pipeline processes the raw marker coordinate files produced by DLC into geometric gait parameters. We then genotyped 138 horses in training for jumping competition by extracting DNA from the bulbs of pulled tail hair and running a PCR-RFLP test. We confirmed these genotypes via sanger sequencing. Of the 138 horses, 58 were purebred Thoroughbreds, 72 were warmbloods, and the remaining 8 were made up of stock horses. The carrier rate was n = 4 in Thoroughbreds, and n = 3in the warmbloods including an Irish Sport Horse, Sillia Argentina, and Holsteiner. We observed a FFS carrier frequency markedly higher in the Thoroughbred population than those reported in previous studies (6.9%, P = 0.015, Χ2 test). A Quadratic Discriminant Analysis then produced standardized coefficient scores for each of the 15 gait parameters to determine the best predictors of genotype within the model. The change in joint extension of both the hind and forelimb were the strongest predictors of genotype and indicated that FFS carriers had greater extension and swing of all 4 limbs. As a result, FFS carriers likely have an altered hoof flight path throughout the stride cycle. Future work will increase the sample size to capture more FFS carriers and will more precisely define the FFS locomotor phenotype. We will also apply this new phenotyping method to investigate changes in gait associated with other genetic variants for connective tissue disorders like HERDA and JEB. Improved quantification of gait parameters, and our understanding of the physiology of this and other known connective tissue disorders in the horse, will aid in future breeding and selection decisions to reduce injury risk and improve performance.

89 Performance of iADF as an internal marker for evaluating forage digestibility in horses

Total fecal collection (TFC) is considered the gold standard for evaluating diet digestibility; however, this method is time consuming, labor-intensive, and requires horses to wear collection harnesses and/or be confined to stalls for prolonged periods. Less frequent sampling of feces can be more practical and less disruptive to the management and routines of certain types of horses (e.g., horses in training, lactating mares, growing horses) but requires the use of a marker to estimate daily fecal output. Indigestible acid detergent fiber (iADF) is routinely used to determine dry matter digestibility (DMD) in cattle but evidence of its effectiveness as an internal marker in horses is limited. This study used 5 mature Quarter Horse geldings to compare fecal output and DMD determined with TFC to that estimated using iADF. Horses were fed alfalfa (Medicago sativa, ALF) or bermudagrass (Cynodon dactylon ‘Coastal’, CBG) hays at 1.6% BW/d in a crossover design. Hays were chosen to represent a large span in fiber concentration (ALF: 38% NDF, 30% ADF; CBG: 70% NDF, 35% ADF). Each period consisted of an 8-d diet adaptation followed by a 3-d TFC. Hays and daily composited fecal samples were analyzed for iADF using 2 methods: in situ incubation in a rumen-cannulated cow and in vitro incubation using equine fecal inoculum from a non-study donor. Samples were incubated for 288 h and sequentially analyzed to determineresidual neutral and acid detergent fibers, with the latter representing iADF. Data were compared using mixed model ANOVA and linear regression. Marker recovery of iADF averaged 98% (SEM 4%) and was similar between iADF methods and hays. Use of fecal inoculum yielded higher estimates of iADF intake (P < 0.01) and iADF excretion in feces (P < 0.01) than the rumen in situ iADF method. Daily fecal output and DMD estimated by rumen in situ iADF (P = 0.27, P = 0.29) and fecal inoculum iADF (P = 0.71, P = 0.79) both agreed with direct determination by TFC. Linear regression of DMD showed a strong relationship between TFC and both iADF methods (P < 0.001), with slightly better prediction when iADF was determined by rumen in situ (y = 0.81x + 7.1; R2 0.85; RMSE 4.8) than equine fecal inoculum (y = 0.79x + 10.0; R2 0.71; RMSE 7.0). Both equations approached a slope of unity and an intercept not different from zero (P > 0.10). Across all methods, DMD of ALF was higher (P < 0.01) than CBG. Findings support use of iADF as a marker to predict DMD of hays in horses. This study measured iADF in samples representing all feces excreted; thus, future work should verify the suitability of iADF as a marker when applied to fecal spot sampling.

Exercise-related changes in the anabolic index (testosterone to cortisol ratio) and serum amyloid A concentration in endurance and racehorses at different fitness levels.

Increased training loads in both human and equine athletes are generally implemented to improve their physical performance. These loads are tolerated only within appropriate training periodization with regard to recovery time. Otherwise, training overload causes failure in the systemic adaptation, which at first leads to overreaching, and progressively to overtraining syndrome (OTS). Exercise endocrinology, and anabolic/catabolic balance as an indicator of athlete performance status and OTS has continued to attract attention. In human medicine, changes in testosterone and cortisol levels, as well as the testosterone to cortisol ratio (T/C; anabolic index), are suggested to be sensitive stress markers. However, there is a lack of research investigating these parameters for use in equine sports medicine. The aim of the study was to investigate the differences in testosterone, cortisol, and T/C in response to a single training session in two types of equine sports: endurance and race, together with serum amyloid A (SAA), the main acute phase response indicator of physical effort, and the overall health status in horses. Two groups of horses were enrolled in the study: endurance (n = 12) and racehorses (n = 32) of different fitness level. Blood samples were obtained before and after the exercise. On average, T increased 2.5 times after the race training in experienced racehorses and dropped in endurance horses regardless the fitness level (p < 0.05). In endurance horses, a decrease in T/C occurred after training in inexperienced horses (p < 0.05). In racehorses, a T/C decrease occurred in the inexperienced group (p < 0.05) and an increase in the experienced (p < 0.01). In conclusion, T/C ratio was found to be a potentially reliable indicator of fitness status especially in racing horses. These findings provide insight into the physiological response of the horses to different types of exercise and the potential use of hormone levels as markers of performance and adaptation.

Homocysteine-Potential Novel Diagnostic Indicator of Health and Disease in Horses.

Homocysteine is an endogenous, non-protein sulfuric amino acid, an intermediate metabolite formed by the methionine transmethylation reaction. Its elevated serum concentration in humans, hyperhomocysteinemia, is a sensitive indicator and a risk factor for coagulation disorders, cardiovascular diseases and dementia. However, the role of homocysteine in veterinary species has not been unequivocally established. Although some research has been conducted in dogs, cats, cattle and pigs, relatively few studies on homocysteine have been conducted in horses. So far, it has been established in this species that homocysteine has an atherogenic effect, plays a role in early embryo mortality and is responsible for the induction of oxidative stress. These preliminary findings support establishing a reference range in a normal population of horses, including horses in training and merit further investigations into the role of this amino acid in health and disease in this species.