The hormones of the adrenal axis help athletes adapt to the stress of training and racing. When performance is poor, dysfunction of this axis is often suspected, but confirming this has been difficult. We have found three hallmarks of chronic stress in horses that are easily monitored: 1) loss of the circadian cortisol rhythm, 2) decrease in corticosteroid-binding globulin and an increase in free cortisol, and 3) reduced ACTH (& hence cortisol) response to a small dose (2 μg) of equine/human corticotropin-releasing hormone (CRH). The presence of some or all of these abnormalities is a good indication that the horse is not coping with the stresses imposed upon him.
The horse has evolved over the millennia to use environmental cues to maximize reproductive efficiency. In domesticating the horse, man has removed or altered some of these cues, often to the detriment of the horse's fertility. This review will describe research of ourselves and others on the hormones controlling reproduction in the mare, and particularly the effect of environmental factors on these hormones and thus upon fertility.
This study was conducted to determine whether there is a relationship between the rankings of sires' breeding values, evaluated based on progeny rating scores, for turf and dirt racing tracks in Thoroughbred racehorses in Japan. Data for analysis were taken from the records of rating scores appearing in the Rating Magazine in May, 1997. Sires with at least 10 progeny having both turf and dirt rating scores were studied along with their progeny. The study populations were 116 sires and 2, 754 progeny for turf racing tracks, and 116 sires and 2, 797 progeny for dirt racing tracks. Sires' breeding values (EPD) were estimated with the BLUP sire model from progeny rating scores for either turf or dirt racing tracks. The fixed effects included in the BLUP sire model were sex, age of progeny and training center, whereas the sire and residuals were treated as random effects. The effect of the sire on rating scores was highly significant (P<0.001) for both kinds of racing tracks. Estimates of heritability for rating scores were 0.29 ± 0.04 at turf racing tracks and 0.18 ± 0.02 at dirt racing tracks. The correlation of a sire's EPD estimated for each kind of racing track clearly showed a positive trend, and the Spearman rank correlation was 0.502 (P<0.001). Based on this result, we conclude that most Thoroughbred stallions produce progeny suited to both turf and dirt racing tracks.
The role of glanders therapy as an alternative to test and slaughter policy was investigated in 13 draught equines (1 horse, 2 mares and 10 mules). The disease was diagnosed clinically and confirmed by isolation of Burkholderia mallei on blood agar and sterile potato slices. Mallein test was positive in 6 (46.15 %) of the 13 animals. All isolates from the 13 equines were sensitive to chloramphenicol, danofloxacin, norfloxacin and co-trimoxazole whereas penicillin and cephalexin were the least effective in vitro antibiotics. These animals were treated for 4 days with Ringer's-lactate-dextrose 500 ml + dimetyl-sulfoxide 60-80 ml intravenously and Inj. Norfloxacin 5% 35-50 ml intramuscularly (1st round of treatment). Five animals were treated again similarly (2nd round) after two weeks of the first round. All treated animals showed a dramatic improvement in the severity of the disease condition which lasted for 2-3 weeks after which the signs rebounded. Even the second round of treatment was met with the same fate. The treatment was not associated with any side-effect except in two cases which suffered injection site swelling. The possibility of a cure in clinical glanders using a longer course of treatment is proposed.
Satellite cells from equine soleus muscles were cultured and the expression of desmin, one of the markers of skeletal muscle cells, was examined. The presence of desmin was detected in some populations of mononucleated cells on day 3 of culture, indicating that equine satellite cells were successfully isolated. On day 5, desmin was localized at the edges of the elongated myotubes but when the equine myotubes matured, no particular localization of desmin expressed diffusely within the cells was seen. Although the significance of such changes in the localization of desmin within the differentiating equine skeletal muscle cells is unknown, these results suggested that desmin may be involved in the growth and development of skeletal muscle in this species.