Adrenocorticotrophic hormone and cortisol levelsduring late pregnancy and post-foaling period in mares

摘要

The aim of this study was to evaluate the trend of adrenocorticotrophic hormone (ACTH) andcortisol levels in mares during peripartum period. Twelve pregnant mares (Group A) were weeklymonitored from the last 6 weeks before foaling (6BF-1BF) until the first 3 weeks after foaling(1AF-3AF). Twelve non-pregnant non-lactating mares constituted the control (Group B). Jugularblood samples were analyzed for plasma ACTH and serum cortisol concentration. ACTH showedhigher values (P<0.05) at 1BF compared to the postpartum data points (1AF, 2AF and 3AF) inGroup A. Cortisol levels were higher (P<0.05) at 1BF and 2BF compared to the 3AF in Group A. Asignificant positive correlation between ACTH and cortisol values was found in mares from GroupA throughout the peripartum period (Pearson’s r=0.40; P=0.0028). The Dunnet’s test showed lowerACTH values in Group A at postpartum data points than control, and higher cortisol levels inGroup A throughout prepartum times and at 1AF than control (P<0.0001). The decrease of ACTHand cortisol levels found during the early postpartum period could indicate a reduced HPA responseto physical and/or psychological stress during this physiological phase. This could help the mare toprotect against stress-associated inhibition of lactation, relieve psychological stress, and enhance herimmune function. Further studies involving the evaluation of prolactin and sex steroid hormonesvalues are needed to fully understand the dynamic hormonal changes occurring in pregnant andlactating mares in order to permit clinicians to make appropriate interpretation of the results.