Effects of stress on reproductive functions in the horse

Abstract

Stress-induced release of glucocorticoids may suppress reproductive functions but effects of stress on fertility have been studied only to a limited extent in the horse. Only when stress is prolonged, it is likely that the secretion of gonadotrophins will be suppressed. For acute stress it is unclear whether reproduction will be affected. Conflicting data exist on the effects of exercise on reproductive function in stallions. An increasing number of stallions are entered into equestrian competitions in parallel to their breeding career. Stallions competing regularly do not differ in plasma cortisol concentrations from stallions used for breeding only. In contrast, in stallions taking part only occasionally in competitions cortisol concentrations are elevated. However, competing has no negative effect on semen quality. Mares are transported frequently during the periovulatory period and increases in plasma cortisol concentrations show that transportation is a stressful event. However, it does not affect the oestrous cycle and pregnancy rate. Stress related to management of mares for artificial insemination (AI) increased secretion of cortisol but does not affect reproductive function.