Increase in ovine plasma cortisol at oestrus and its relation with the metabolic status during the sexual cycle in sheep

Metabolic status is an important factor modulating reproductive function in ruminants. Evidence from our group has led to the concept that reproductive hormones, in turn, were capable of modulating metabolic responses. In the present study, cortisol plasma concentrations have been determined in the peri-oestrus of cyclic ewes fed half or all of their maintenance requirements, and related to concentrations of insulin, insulin-like growth factor 1 (IGF-1), leptin, glucose and non-esterified fatty acids (NEFA). Cortisol concentrations experienced a six-fold rise at oestrus, independently of the level of nutrition. Moreover, they were positively correlated with glucose and IGF-1 concentrations. It is suggested that the cortisol increase at oestrus could be due to oestrogenic action in the adrenal cortex, and that it could explain some of the metabolic fluctuations observed before.

Keywords:

• cortisol
• oestrus
• sheep
• undernutrition