Plasma beta-endorphin and adrenocorticotrophin in young horses in training
Version of Record online: 10 MAR 2008
Australian Veterinary Journal
Volume 68, Issue 11, pages 359–361, November 1991
How to Cite
McCARTHY, R., JEFFCOTT, L., FUNDER, J., FULLERTON, M. and CLARKE, I. (1991), Plasma beta-endorphin and adrenocorticotrophin in young horses in training. Australian Veterinary Journal, 68: 359–361. doi: 10.1111/j.1751-0813.1991.tb00736.x
- Issue online: 10 MAR 2008
- Version of Record online: 10 MAR 2008
- Accepted for publication 1 August 1991
SUMMARY A controlled period of submaximal exercise on a treadmill was used as a standardised stress test in 6 young horses to monitor the effects of training. Circulating plasma concentrations of immunoreactive beta-endorphin (IR β-EP) were measured before, during and after the exercise period. The stress test was conducted on 3 occasions during an intensive training program lasting 14 weeks. In week 3 a marked increase in plasma IR β-EP (P=0.003) was demonstrated as a result of training, but by the last exercise test performed in week 9 no significant increase in plasma IR β-EP concentrations could be detected. During the training period the basal concentrations of plasma IR β-EP significantly decreased (P=0.0059). Plasma adrenocorticotrophin (ACTH) did not increase during exercise, although there was a trend of decreasing basal plasma ACTH by the end of the training period.
It was concluded that a standardised work test acted as a mild stress to unfit horses, but as the horses' fitness increased the hormonal response to exercise diminished. Basal plasma β-EP concentrations were decreased with increasing fitness.