Alteration of Ingestive Behavior and Plasma Metabolites by Estrogen in Ovariectomized Goats

Abstract

Ovariectomized goats were treated with subcutaneous implants containing ovarian steroid hormones and their effects on ingestive behavior and plasma metabolite concentrations were examined along with those on reproductive function. Sequential administrations of progesterone (P) and estradiol (E) reproduced steroidal milieu during the luteal through the follicular phases. Around 35 hours after the commencement of the E administration, estrous behavior appeared, and almost simultaneously the luteinizing hormone surge occurred. During the estrous period, amount of food intake and duration of rumination markedly decreased, whereas plasma concentrations of glucose and free fatty acid increased. These changes lasted until the E-implant was removed. The E administration without P pretreatment induced similar changes in reproductive, ingestive and metabolic parameters, although the occurrences of these were all advanced. In contrast, the administration of P alone had no such effect on any parameter. These results demonstrate that estrous behavior is accompanied by changes in feeding behavior and metabolism, and suggest that E is playing essential roles to prepare female for mating by coordinating diverse physiological functions in the goat.