LH pattern and ovarian response in ovsynch-synchronized superovulated goats induced to ovulate with GnRH or hCG

The intention of the present investigation was to compare a GnRH agonist and hCG as ovulation inducing agents to apply fixed-time insemination in ovsynch synchronized superovulated goats. Three groups of 17 does of the Boer goat breed were synchronized, superovulated and ovulation induced with a GnRH analog, hCG or physiological saline, followed by mating and non-surgical embryo collection. Part of the does were provided with subcutaneous progesterone implants after mating to compensate for frequently occurring premature corpus luteum regression. Estrus detection was conducted with aproned bucks, ovarian function was monitored sonographically and by progesterone analyses and blood samples were drawn to generate LH profiles. Practically all does responded to treatment and occurrence and duration of estrus as well as the ovulatory response were unaffected by treatment. The LH surge provoked by administration of the GnRH analog buserelin emerged within 1.0 h and was closely synchronized, significantly more so than after administration of hCG or physiological saline, commencing after 11.8 and 14.9 h, respectively, with no significant differences amongst each other. It would seem that hCG is not effective in bringing about a LH surge. The interval between commencement of the LH surge and ovulation was, across treatment groups, 24.2 h with no significant difference among groups. Ovulatory response and yield of transferable embryos obtained by nonsurgical collection were modest with no significant differences among groups.