Responses of Horses of Various Breeds to a Sympathetic Training Method

The objective of this study was to compare the responses of horses of different breeds to a sympathetic training method used during an initial training period, before the horses started their first racing season. Subject animals were 72 horses: 24 Thoroughbreds, 24 Purebred Arabians, and 24 Angloarabs. Each breed group consisted of 12 colts and 12 fillies. The sympathetic method used to train the horses lasted for 3 days in a row, one session per day. Training was divided into five stages, each stage made up of particular tasks to be achieved. The horse’s reaction to the training was measured with the length of time (seconds) necessary to complete a stage and the horse’s heart rate (bpm) during the stages. Data were analyzed by using multifactorial analysis of variance, taking into account the effect of horse breed, sex, and training session. Results showed that horses of various breeds had different responses to the training. The Angloarabs took the longest to complete the training stages. The 3-day training period caused the highest reaction in the Angloarabs, and the 3-day period was too short to allow for more than half of them to be mounted. Heart rate was more increased in Purebred Arabian and Angloarab fillies than in colts, which shows that fillies require particularly gentle treatment.     

Emotional Response to Novelty and to Expectation of Novelty in Young Race Horses

The aim of this study was to estimate the emotional response to novelty and to expectation of novelty in young race horses. The novelty in this study was the first training on an automated horse walker at a new training center. To estimate the level of emotionality in horses, the telemetric measurement of heart rate (HR) was used. A hypothesis was developed that expectation of novelty can be as exciting for horses as a novelty test. In this study, 40 horses were studied just before and then during their first walk on an automated horse walker. They were divided into four groups, with 10 horses in each group. These groups were as follows: (1) 1.5-year-old Thoroughbred colts, (2) 1.5-year-old Thoroughbred fillies, (3) 2.5-year-old Purebred Arabian colts, and (4) 2.5-year-old Purebred Arabian fillies. HR was measured at rest before exercise, during handling and moving the horse from the stable, while walking on the automated horse walker for about 20 minutes, while moving the horse from the walker to the stable, and at rest after exercise. HR response to the anticipation of novelty was higher in colts than in fillies, particularly in the group of Thoroughbreds.     

Retrospective analysis of 50 cases of guttural pouch tympany in foals

Between 1994 and 2001, guttural pouch tympany was diagnosed in 51 foals; there were approximately three times as many fillies as colts, of Arabian, different German warmblood breeds and Western horse breeds. There were significantly more Arabian and paint horse foals than expected in comparison with the breed distribution of the foals hospitalised at the Clinic for Horses. The foals' breed and sex did not influence the age of onset, the type and severity of the clinical signs or the recurrence rate. A surgical laser technique was used on 50 of the foals; in 35 cases only one surgical treatment was necessary, in seven cases a second operation was required during the foal's initial period of hospitalisation, and in eight cases a second operation was performed during a second period of hospitalisation. Long-term follow-up information was obtained for 44 of the 50 treated horses; 24 of them were under two years of age and 20 were over two years of age. In six horses, no follow-up information was available. Four horses were euthanased for reasons unrelated to the condition or its treatment. The horses over two years of age were in training or were being used for competitions in dressage or jumping or for breeding purposes, and in only one of them was an adventitious respiratory noise reported. All the horses up to two years of age were reported to be healthy.     

Age- and gender-related variations in hematology, clinical biochemistry, and hormones in Spanish fillies and colts

In order to assess which laboratorial parameters need specific age- and/or gender-related reference values, hematological and biochemical profiles (including hormones) were performed in 205 Spanish foals of 5 groups: A (1-2 months; 20 fillies, 10 colts), B (2-3 months; 24 fillies, 18 colts), C (3-6 months; 25 fillies, 16 colts), D (6-9 months; 20 fillies, 23 colts) and E (9-12 months; 25 fillies, 15 colts). Additionally, 120 adult horses were sampled in order to establish baseline data for this breed in our laboratory. Group E had lower red blood cell number and mean cell volume than B, C and D, and neutrophil count was lower in A. Albumin was lower in A than in D, lactate was higher in B, C and D, CK, AST and K were higher in C. In D and E, cortisol was lower and adrenaline was higher. Urea progressively increases, whereas ALP decreases with age. Packed cell volume was higher in fillies of group A, creatinine was higher in colts of group E and fillies of groups B, C, and D had higher aldosterone than colts. In comparison to Spanish adult horses, mean cell volume, albumin, urea, CK, AST, LDH, and ALP requires specific ranges for foals.     

An investigation of the effect of hesperidin complex and lemon bioflavonoid complex on growth and development of thoroughbred horses

The objective of this study was to determine the effect of Hesperidin Complex and Lemon Bioflavonoid Complex (HC/LBC) on the growth and development of thoroughbred horses. The trial involved twenty-four foals (12 colts, 12 fillies) allotted to treatment shortly after weaning. The study was conducted for a 342-d growing phase and a 153-d training phase, or a total of 495-d. The HC/LBC was included in the test diet at a level calculated to supply the compound at 55 mg X kg body weight-1 X d-1. During the growing phase, average daily gain of colts that received HC/LBC was higher (P less than .05) than gain of control fillies but not different from that of treated and control colts. No differences (P greater than .05) in daily gain due to treatment were observed during the growing phase, training phase, or the data for the combined growing and training phases. Differences between treatments in changes in height at the withers and knees during the growing phase were not significant. In the training phase, average daily height change values for colts was higher (P less than .05) than that of fillies; however, these differences were not related to diet treatment. Radiographs were taken of the epiphyseal plate of the knee initially and at approximately 120-d intervals. No differences (P greater than .05) were noted between diet treatments through d 365 of the trial. Radiographs taken upon termination of the trail (495 d) showed a difference (P less than .05) favoring fillies over colts, but no differences related to diet treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in serum muscle enzyme levels associated with training schedules and stage of the oestrous cycle in Thoroughbred racehorses

Blood samples were collected twice weekly over a nine month period from 24 Thoroughbred racehorses in training at Newmarket to study the effects of daily training schedules and stage of oestrous cycle on serum enzyme levels and clinical signs of equine exertional myopathy. The sampling period extended from November to July and was performed between 16:00 h and 18:00 h so as to be at least 6 h after exercise. Serum creatine kinase, aspartate aminotransferase and plasma progestogen concentrations were measured. All horses were subjected to a similar traditional training programme. The study demonstrated marked fluctuations in serum muscle enzyme concentrations which were more pronounced in two-year-old fillies than three-year-old fillies and colts. There was no correlation, however, with the stage of oestrous cycle. It was concluded that some degree of muscle cell damage, which results in a variable increase in serum creatine kinase levels, occurs in all horses following light exercise after a rest day. Traditional flat race training may not be ideal in this respect and it is suggested that, for horses with an observed tendency towards exertional myopathy, more consistent and longer periods of less strenuous exercise may be advantageous.     

Prevalence and distribution of radiographically evident lesions on repository films in the hock and stifle joints of yearling Thoroughbred horses in New Zealand

AIM: To characterise the prevalence and distribution of radiographic changes in the hocks and stifles of Thoroughbred yearling colts and fillies in New Zealand and compare them with other populations of young horses. METHODS: Repository radiographs taken in New Zealand for the 2003-2006 Thoroughbred national yearling sales were evaluated by two individual readers. The distribution of radiographic changes was classified as left side only, right side only, or bilateral. Lesions were categorised by type, location, and sex of the yearling. Complete sets of hock and stifle radiographs of 1,505 yearlings were evaluated. RESULTS: Osteophytes or enthesophytes were seen radiographically in the distal tarsal joints of 460/1,505 (31%) horses. Osteochondrosis was seen in the tibiotarsal joint of 66/1,505 (4%) horses, and in the femoropatellar joint of 40/1,505 (3%) horses. Radiographic lucency in the distal or axial aspect of the medial femoral condyle was seen in 247/1,505 (16%) horses, and lucencies consistent with subchondral cyst-like lesions were seen in 26/1,505 (2%) horses. No significant difference was seen in the proportion of colts and fillies with radiographic changes in the hock or stifle. The prevalence of osteochondrosis and subchondral cyst-like lesions in the stifles of the yearlings examined were similar to those reported in Thoroughbred yearling sale horses in the United States of America (USA). The prevalence of changes in the distal tarsal joints was similar to those reported in Standardbred and Thoroughbred yearlings from Scandinavia and the USA. CONCLUSIONS: There was no significant difference in the prevalence of osteochondrosis in the hock and stifle, lucencies in the distal medial femoral condyle, or radiographic changes in the distal tarsal joints between colts and fillies. CLINICAL RELEVANCE: Establishment of the normal prevalence and distribution of radiographic changes in the hocks and stifles of Thoroughbred yearlings in New Zealand will allow comparison with populations of young horses in other countries. Knowledge of the normal prevalence will assist veterinarians to identify abnormally high or low prevalences on individual farms, to further investigate the pathogenesis of the lesions.     

Influence of age and sex on serum osteocalcin concentrations in horses at weaning and during physical conditioning

Three experiments were conducted to evaluate serum osteocalcin concentrations in normal weanling and yearling Quarter Horses. In Experiment 1, jugular blood samples were taken at 3 hr intervals for 24 hr to evaluate diurnal changes in serum osteocalcin concentration of foals (n=3) and yearlings (n=5). In Experiment 2, twelve Quarter Horse foals were weaned at 4 months of age to determine the influence of sex, weaning and method of weaning of serum osteocalcin concentration. The third experiment utilized fifteen yearling Quarter Horses (7 geldings, 8 fillies) in a two-phase trial to evaluate normal peripheral osteocalcin concentration in sedentary and exercising horses. In Experiment 1, there was no detectable variation (P>.05) in serum osteocalcin concentration during the 24 hr sample period in either age group. In Experiment 2, colts had greater (P<.05) osteocalcin concentrations than fillies at weaning. Method of weaning did not alter mean serum osteocalcin concentration (P>.1). Serum osteocalcin concentrations declined (P<.05) in all horses following weaning but returned to preweaning levels within one week. In Experiment 3, sedentary horses had similar (P>.1) osteocalcin concentrations on d 0, 45 and 90. Serum osteocalcin concentrations of sedentary horses were not affected by sex (P>.1). During exercise, fillies had greater (P<.05) osteocalcin concentrations than geldings. Serum osteocalcin concentrations of all horses declined linearly (P<.0001) during the 90 d exercise period. Osteocalcin may be useful as a tool to assess bone metabolism during growth and physical conditioning in horses. However, variability in serum osteocalcin concentrations due to age, sex and level of activity suggest that these factors must also be considered.     

Genetic predictions of racing performance in quarter horses

Research on the racing performance of quarter horses has been used to develop genetic prediction summaries on all horses with at least one start on record at the American Quarter Horse Association. In the 1987 summary, records from a total of 212,065 horses were used to give genetic predictions on stallions, mares, geldings, fillies, and colts. A reduced animal model was used that incorporated the repeated records of individuals. The individual race was the contemporary group after the data were adjusted for distance, sex, and age. Estimates of heritability of .24 and repeatability of .32 suggest that increased racing performance can be achieved if the predictions are used by breeders. Continued research in variance component estimation includes the genetic covariances among the several distances, maternal influence, and genetic parameters for racing longevity.     

Gestational length in Carthusian broodmares: effects of breeding season, foal gender, age of mare, year of parturition, parity and sire

The length of gestation in Carthusian broodmares was calculated on the basis of 339 spontaneous full-term deliveries taking place in the 8-year period 1998-2005 from 158 broodmares and 29 stallions in a major farm of Spanish horses of Carthusian strain in southern Spain. Ultrasonography was used to determine follicular dehiscence, 1st day of pregnancy and to confirm conception in mares. Mean GL was 332.4 +/- 12.1 days, and a normal interval of 297-358 days was established for this breed. GL records were grouped on the basis of foal sex (colts or fillies), mating month (between November and January; February and April; May and July), age of the mare (4 to 7 years; 8 to 12 years; 13 to 17 years), breeding year, stallion and parity (primiparous vs. multiparous). GLs were 12.9 days shorter in mares mated between May and July than those mated between November and January and 15.3 days in mares mated between February and April (p < 0.001). Mares aged between 8-12 years had 5.3 days shorter GLs than those aged between 13-17 years (p < 0.05). Pregnancy was significantly 5.7 days longer when the mare gave birth to colts than fillies (p < 0.05). GL was 14.5 days longer in primiparous than in multiparous mares ( p < 0.001). No statistical differences in GL were found between the studied years. This study shows the influence of certain stallion on GL.     

Inheritance of recurrent exertional rhabdomyolysis in thoroughbreds

OBJECTIVE: To develop a diagnostic test for recurrent exertional rhabdomyolysis (RER) in Thoroughbreds that relied on in vitro contracture of muscle biopsy specimens and determine whether the inheritance pattern of RER diagnosed on the basis of this contracture test was consistent with an autosomal dominant trait. DESIGN: Clinical trial. ANIMALS: 8 adult horses with RER and 16 control adult horses for development of the contracture test; 23 foals for inheritance of RER. PROCEDURE: External intercostal muscle biopsy specimens from the 24 adult horses were tested for contracture in response to halothane and caffeine, and criteria for a positive test result were determined. These criteria were then applied to results for the 23 foals to determine whether they had RER. Simple segregation analysis was performed to determine whether results were consistent with a dominant pattern of inheritance. RESULTS: Results of the contracture test were positive for 5 of the 12 colts and 4 of the 11 fillies. Results of segregation analysis were consistent with an auto-. somal dominant pattern of inheritance. Two sires with RER produced colts with RER, supporting the hypothesis that RER had an autosomal, rather than an X-linked, inheritance pattern. In addition, in 1 instance, an unaffected colt was produced by 2 affected parents, which was not consistent with a recessive mode of inheritance. CONCLUSIONS AND CLINICAL RELEVANCE: Although the expression of the RER trait is influenced by sex, temperament, and diet, among other factors, results from the in vitro muscle contracture test and this breeding trial suggest that RER in Thoroughbreds can be modeled as a genetic trait with an autosomal dominant pattern of inheritance.     

The Effect of Different Physical Exercise on Plasma Leptin,Cortisol, and Some Energetic Parameters Concentrations in Purebred Arabian Horses

Leptin is a hormone that coordinates food intake, energy expenditure, and metabolic rate; it is, however, unknown how exercise influences plasma leptin concentration in horses. The aim of the study was to evaluate the exercise-induced changes in plasma leptin concentration in purebred Arabian horses competing in races and endurance rides. A total number of 26 horses (12 purebred Arabian racehorses aged 3–5 years and 14 endurance horses aged 7–14 years) were studied during performing routine physical exercise. From each horse, blood samples were collected at rest and immediately after the exercise session. Concentrations of plasma leptin, cortisol, lactic acid, uric acid, triacylglycerols, glycerol and free fatty acids were determined. Exercise-induced increase in cortisol and free fatty acid values were higher in endurance horses than in racehorses. Neither endurance nor race exercises influenced the plasma leptin concentration. Further research is needed to elucidate the effects of different types of exercise on leptin synthesis and secretion in horses.     

Decreased erythrocyte potassium concentration associated with exercise-related myopathy in horses

To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were pastured and not in training. Creatine kinase activity in serum from horses of groups 1 and 2 was also measured. The mean P [K+] was not significantly different between groups, whereas the mean RBC [K+] was significantly (P less than 0.01) lower in group-1 fillies vs group-2 fillies and group-3 horses. Group-1 fillies also had markedly high serum creatine kinase activity. Results of the study revealed significantly lower RBC [K+] in horses that had had signs of myopathy within the preceding 48 hours. This does not prove a causal relationship between RBC potassium depletion and myopathy, but does suggest that decreased RBC [K+] may be observed in horses with exercise-related myopathy.     

Effects of exercise on serum amino-transferase activity and pyridoxal phosphate saturation in Thoroughbred racehorses

Aminotransferase activities were measured in the serum of two- to three-year-old Thoroughbred fillies and colts during a four week period of peak training for flat racing. Aspartate aminotransferase (AspAT, EC 2.6.1.1), mitochondrial aspartate aminotransferase (m-AspAT) and alanine aminotransferase (AlaAT, EC 2.6.1.2) activities in serum were measured and the relative proportions of apoenzyme and holoenzyme were determined. The aminotransferase activities were increased only slightly immediately following exercise. This small and immediate post exercise increase in activity did not vary greatly over the period of peak training. Measured in the presence of exogenous pyridoxal 5'-phosphate, mean enzyme activities (iu/litre at 30 degrees C) before exercise were: AspAT, 291; m-AspAT, 13; AlaAT, 18. After exercise they were: AspAT, 317; m-AspAT, 16; AlaAT, 23. Nearly all of the AspAT activity was present in the holoenzyme form (94 per cent holoenzyme) indicating excellent vitamin B6 status in these animals. Paradoxically, the AlaAT in serum from the same highly trained Thoroughbred horses was poorly saturated with pyridoxal phosphate, with nearly half of the AlaAT in most horses present in the inactive apoenzyme form (61 per cent that of holoenzyme). It is critical therefore, that exogenous pyridoxal phosphate be included in aminotransferase assays to determine the amounts of enzyme release into the peripheral circulation.     

Competition Horses Housed in Single Stalls (I): Behavior and Activity Patterns during Free Exercise According to Its Configuration

Although welfare of animals has become more important, housing horses in systems that limit natural behavior patterns is still widespread. Single stalls are the predominant housing system in Germany, especially for competition horses. Free exercise on fields or paddocks helps to improve welfare for the animals, but allowing it is not taken for granted by many horse keepers. In the present study, three common management practices were investigated with regard to their effect on the behavior of six competition horses housed in single stalls: 2-hour turnout after training in groups of two horses (group turnout [GT]), solitary turnout (ST) after training for 2 hours, and no turnout (NT) in addition to training. The aim of the study was to determine the differences in the horses’ behavior during turnout, training, and in the stable caused by the treatments. This article focuses on the behavior and activity patterns during turnout. The horses’ behavior was observed directly by the scan sampling method (5-minute interval), and the distance covered during turnout was measured by global positioning system devices. During turnout, the horses spent most of the time eating. After 1 hour of being turned out, eating decreased, and occupation, locomotion, and social interaction increased. When turnout was allowed in groups (GT), the horses spent more time in social interactions and less time walking and trotting than in ST. Therefore, they also covered a greater distance in ST than in GT. The distance covered in ST also showed a greater deviation both within and between days compared with GT.     

Plasma aspartate aminotransferase and creatine kinaseactivities in thoroughbred racehorses in relation to age, sex, exercise and training

In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase(AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2HΔ) and the 24H and PRE samples (24HΔ) was also calculated. Age had a significant effect on all measured and calculated parameters for colts (C), apart from 24HΔ CK but showed no effect in the fillies (F). Sex only had a significant effect in the 3yo in the 2HΔ CK. In the 2yo, significant effects of sex were found for both CK and AST in the PRE, 2H and 24H samples. The effect of month varied according to the classification group with only the 2yoC not showing any significant effect on any parameter. Fillies were, in general, more likely than colts to show greater than a twofold increase in CK activity at 2H post-exercise and the number of animals showing such an increase decreased as the season progressed. Very little change in AST activities occurred with exercise.     

Aerobic Training, But Not Creatine, Modifies Longissimus Dorsi Muscle Composition

The goal of this study was to investigate by means of an ultrasound examination the composition of the longissimus dorsi muscle in 12 purebred Arabian horses submitted to aerobic training for 90 days, with and without creatine supplementation. Creatine supplementation was carried out by daily administration of 75 g creatine monohydrate mixed into the ration during 90 days of training. Physical conditioning was conducted on a high-performance treadmill, and training intensity was stipulated by calculating the velocity at which blood lactate reaches 4 mmol/l, determined monthly for each animal. The individual intensity of physical force was established at 80% of velocity that resulted in a blood lactate level of 4 mmol/l. The cross-sectional area and the thickness of the layer of fat of the longissimus dorsi muscle were measured for each group at the end of 8 months of inactivity and after 30, 60, and 90 days of training without (control groups) or with creatine supplementation (experimental groups). The results showed that aerobic training combined with or without creatine supplementation caused significant longissimus dorsi hypertrophy and reduction in the thickness of the fat layer. No beneficial effect from prolonged creatine supplementation on the body composition of horses was detected.     

Ultrasound Measurements of the Dorsal Subarachnoid Space Depth in Healthy Trotter Foals during the First Week of Life

The aim of this study was to determine ultrasonographic measurements of the depth of the dorsal subarachnoid space in healthy foals so as to obtain reference values. The depth of the dorsal subarachnoid space was recorded in 50 trotter foals at day 1 (D1), 4 (D4), and 7 (D7) after birth, measuring the distance between the dura mater and the dorsal portion of the pia mater at the level of the cisterna magna, both in cross-sectional and longitudinal scans. Average, standard deviation, minimum and maximum values were calculated. Wilcoxon signed rank test was applied to verify data distribution. Analysis of variance (ANOVA) for repeated measurements and Bonferroni test as post hoc were applied to verify differences among D1, D4, and D7, both for cross-sectional and longitudinal scans. Student’s t-test for unpaired data was performed between fillies and colts to verify differences related to gender. Significance level was set at P < .05. Cross-sectional measurements were 7.2 ± 0.7 mm at D1, 7.4 ± 0.7 mm at D4, and 7.5 ± 0.6 mm at D7, whereas longitudinal measurements were 7.3 ± 0.6 mm at D1, 7.6 ± 0.6 mm at D4, and 7.6 ± 0.5 mm at D7. Differences in dorsal subarachnoid space depth were observed at D1 versus D7, both for cross-sectional and longitudinal scans, whereas no differences were found between fillies and colts. In this study, a reference range for the depth of the dorsal subarachnoid space has been reported in foals.     

Fumonisin B1 levels associated with an epizootic of equine leukoencephalomalacia

During the fall of 1989, an episode of equine leukoencephalomalacia involved 18 of 66 purebred Arabian horses at a breeding/training stable in Arizona. Of the 18 horses affected, the condition was fatal in 14. These horses, as well as 48 unaffected horses, had been fed a diet containing a substantial amount of white corn screenings. Gross pathologic findings included liquefactive necrosis in parts of the cerebral white matter and hemorrhagic foci of various sizes in the brain stem. Histopathologic findings included rarefied white matter with pyknotic nuclei and eosinophilic cytoplasm. Thin-layer chromatography, high-performance liquid chromatography, and gas chromatography/mass spectroscopy were utilized to identify and quantitate fumonisin B1 in 3 samples of corn from the farm. Concentrations of fumonisin B1 range from 37 to 122 ppm. Fumonisin B2 was also detected. Using information on diet, animal weights, and feeding practices, estimates of total fumonisin B1 dosage were determined. This is the first definitive report on equine leukoencephalomalacia and associated fumonisin B1 concentrations.