Cortisol and Postpartum Luteal Function in Cattle

The present study investigated serum cortisol in response to postpartum ovarian resumption and luteal function. Postpartum ovarian resumption was detected based on a rise in progesterone (P4) concentrations during three weeks after calving. Twenty two Holstein cows in a semi-closed dairy farm in Qena city, Egypt were used. The study was carried out from late March to early June; the period characterized by a good temperature humidity index (THI) and absence of heat stress. According to the concentrations of P4 in serum (P4 >1.0 ng/mL), 11 of the 22 cows resumed the ovarian activity within three weeks after calving (ovarian resumption cows). No effect of THI was found during the postpartum period of study on the concentrations of P4, cortisol and cholesterol in the ovarian resumption or non-ovarian resumption group. In the former, cholesterol showed a significant correlation with both P4 (r=0.405, P