Abstract: The social behavior of feral horses was studied in the western United States. Stable harem groups with a dominant stallion and bachelor hermaphrodite hermaphrodite groups occupied overlapping home ranges. Groups spacing, but not territoriality, was expressed. Harem group, stability resulted from strong dominance by dominant stallions, and fidelity of group members. Eliminations of group members were usually marked by urine of the dominant stallion. Hermaphrodite-hermaphrodite aggression involved spacing between harems and dominance in bachelor groups. Marking with feces was important in hermaphrodite-hermaphrodite interactions. Foaling occurred in May and early June, following the post-partum estrous. All breeding was done by harem stallions. Young were commonly nursed through yearling age. These horses showed social organizations similar to other feral horses and plains zebras.

Abstract: REASONS FOR PERFORMING STUDY: There is little information about the prevalence of gastric ulcers in Standardbred trotters and potential correlations between ulcers and various traits, e.g. age, sex, performance, temperament and feeding regimens, need further elucidation. OBJECTIVES: The prevalence of ulcers in the gastric squamous mucosa of Swedish Standardbreds was estimated and the associations between ulcer score and age, sex, performance, temperament and feeding regimens were determined. METHODS: Eighty Swedish Standardbreds in active race training, trained by 9 different trainers, underwent gastroscopy. Information on age, gender, status of training, performance over the last 4 months compared with the trainer's expectations before that period, behaviour, eating habits, feed type, bedding type, time spent outdoors per day and medical treatment during the last month was collected. Gastroscopy was performed and lesions in the squamous gastric mucosa were scored from 0 to 4 (0 = no lesions; 4 = > 5 lesions with haemorrhage, > 10 lesions with no haemorrhage, or a large area of diffuse loss of surface epithelium). RESULTS: Twenty-four (30%) of the horses had no lesions in the squamous mucosa, 22 (27.5%) had a score of 1; 21 (26.2%) score 2; 9 (11.2%) score 3; and 4 (5%) score 4. Horses that were in preparatory training and those that had raced during the last month were significantly more affected than horses that were fit for racing but had not raced during the last month, using a logistic regression model with trainer incorporated as a random effect. CONCLUSIONS: The study confirmed a high prevalence of ulcers in the gastric squamous mucosa of Standardbreds in race training. Of the studied parameters only status of training showed a significant association with gastric ulcers of the squamous mucosa. POTENTIAL RELEVANCE: Gastric ulceration is a common disease and diagnosis should be made by endoscopic examination of the gastric mucosa, since parameters such as age, gender, performance, behaviour, eating habits provide only weak clues as to which horses might be affected. Further studies are needed to determine the aetiology of the syndrome and to find ways to reduce, if possible, the frequency of gastric ulcers.

Abstract: Oxytocin (OT) promotes social and reproductive behaviors in mammals, and OT deficits may be linked to disordered social behaviors like autism and severe anxiety. Male rat sexual behavior is an excellent model for OT regulation of behavior, as its pattern and neural substrates are well characterized. We previously reported that OT microinjected into the medial preoptic area (MPOA), a major integrative site for male sexual behavior, facilitates copulation in sexually experienced male rats, whereas intra-MPOA injection of an OT antagonist (OTA) inhibits copulation. In the present studies, copulation on the day of sacrifice stimulated OTR mRNA expression in the MPOA, irrespective of previous sexual experience, with the highest levels observed in first-time copulators. In addition, sexually experienced males had higher levels of OTR protein in the MPOA than sexually naïve males and first-time copulators. Finally, intra-MPOA injection of OT facilitated mating in sexually naive males. Others have reported a positive correlation between OT mRNA levels and male sexual behavior. Our studies show that OT in the MPOA facilitates mating in both sexually naive and experienced males, some of the behavioral effects of OT are mediated by the OTR, and sexual experience is associated with increased OTR expression in the MPOA. Taken together, these data suggest a reciprocal interaction between central OT and behavior, in which OT facilitates copulation and copulation stimulates the OT/OTR system in the brain.

Abstract: REASONS FOR PERFORMING STUDY: Overstrain injuries to the superficial digital flexor tendon (SDFT) and suspensory ligament (SI) are among the most common musculoskeletal injuries which contribute to the considerable wastage of racing Thoroughbreds. Many epidemiological studies have demonstrated the prevalence of and risk factors for tendon injury when racing but have not included those injuries sustained during training. However, since tendon injury during training is seen commonly in clinical practice, it is appropriate to determine the overall prevalence of tendon injury sustained during both training and racing. OBJECTIVE: To determine the prevalence of overstrain injury to the SDFT and SL during training and racing among Thoroughbred flat racehorses in Japan in 1999. METHODS: A retrospective study was performed using a sample population of 10,262 Thoroughbred racehorses. The medical information database of Thoroughbred racehorses registered by the Japan Racing Association (JRA) in 1999 was analysed for SDFT and SL overstrain injury diagnosed by a veterinarian employed by JRA during training and racing. Jump racehorses were excluded from this study. RESULTS: The prevalence of forelimb SDFT tendonitis and SL desmitis was 11.1% (1130 cases) and 3.61% (370 cases) of the population, respectively. In the hindlimb, there were 0.06% (6 cases) and 0.14% (14 cases), respectively. Risks of SDF tendonitis in the forelimb in 3-year-olds or older horses were significantly higher than in 2-year-olds. In contrast, the risk of SL desmitis in the forelimb at age 3 and 4 years was 2.23 and 2.11 times higher, respectively, than in 2-year-olds, but this increased to 5.07 times in those age > or = 5 years. Entire males were at greater risk in comparison to females and geldings. CONCLUSIONS: The results suggest that the prevalence of SDF tendonitis and SL desmitis in the forelimb was associated with the horse's age and sex. The prevalence of SL desmitis increased further with age compared with SDF tendonitis, possibly reflecting a more rapid accumulation of degeneration in this structure. POTENTIAL RELEVANCE: The age-related risk demonstrated in this study provides further support that overstrain injuries are associated with accumulated degeneration. These data provide a valuable resource for further research into the aetiology of tendon injury in the racehorse.

Abstract: Summary The aim of this study was to investigate the effect of gonadotrophin-releasing hormone (GnRH) immunisation on mature stallions that had been used for breeding. Four Standardbred stallions were used in the study: 3 experimental animals and 1 control animal. Semen was collected regularly, i.e. twice/week, during the 4 months prior to the experimental period. The stallions were immunised against GnRH with a GnRH-BSA conjugate. Equimune was used as the adjuvant. The stallions were immunised on 5 occasions, 4 at 2 week intervals, and the fifth 4 weeks after the fourth. Blood samples were taken once a week for analysis of GnRH antibody titre and every third week for testosterone and oestrone sulphate analyses. Semen was collected once a week, and libido and sexual behaviour were observed. Ejaculate volume, sperm concentration, total number of sperm in the ejaculate, sperm motility and sperm morphology were evaluated. Testicular size was measured once a week. At the end of the study, the stallions were castrated, and a histological examination of the testes performed. All immunised stallions produced antibodies against GnRH, and plasma testosterone concentration decreased. However, the effect of immunisation varied between stallions. In 2 of the stallions, high levels of antibodies were found, while in the third, the level was moderate. Four weeks after the first immunisation, a decrease in libido was observed. Two months after the first immunisation, marked changes in semen quality were observed in the 2 stallions with high antibody titres. Fourteen weeks after the first immunisation, the total number of sperm/ejaculate had decreased from >8.6×109 to<2.7×109, sperm motility from >59 to<10% and the frequency of morphological normal spermatozoa had decreased from >60 to<14%. The dominating abnormalities were abnormal head shapes, proximal cytoplasmic droplets and detached heads. In the third stallion, only slight changes in semen quality were found. No changes were observed in the control stallion. Decreases in testicular size were noted in all of the experimental stallions. Pronounced histological alterations in the testes were observed in 2 of the stallions. It is concluded that the vaccine was effective in stimulating production of GnRH antibodies and in suppressing testicular function and androgen secretion. However, there was an individual variation in the responses among the stallions and, further, libido was not totally suppressed.