Cortisol changes in pregnant and post-partum ewes: effects of single or twin births

Cortisol is a reliable physiological index of stress in sheep. Pregnancy and post-partum conditions, the influence of a single or a twin birth, and simultaneous milking may represent significant sources of stress for the mother and lambs. We characterized the adrenal response in ewes during late pregnancy and post-partum by accounting for the possible influence of single or twin birth on changes in circulating cortisol levels. Cortisol levels were in agreement with normal physiological ranges reported for sheep and with previous data obtained from lactating ewes. There was a significant increase in cortisol levels in postpartum compared with pregnancy, and there was a comparable trend between Comisana and Pinzirita crossbreds. With regard to the influence of single or twin birth, post-partum cortisol levels were higher in ewes with both single and twin birth. In addition, post-partum cortisol levels were increased in ewes with male births and both female and male births.