Follicular response and oocyte production following variations in ovarian stimulation in goats

Abstract

In this study, goats were subjected to ovarian stimulation protocols to evaluate possible differences in ovarian follicular responses and oocyte production. Two experiments were conducted to assess the effects of hormonal protocol duration (seven or twelve days) and number of follicle stimulating hormone (FSH) applications (one or five doses). All animals received intravaginal sponges saturated with 60 mg medroxyprogesterone acetate and an application of 125 μg cloprostenol 72 h before the sponges were removed. For ovarian stimulation, 120 mg FSH was applied in a single dose 36 h before laparoscopic follicular aspiration (LOPU) or in five doses (30, 30, 20, 20, and 20 mg) at 12 h intervals, with the last dose applied 36 h before LOPU. In the first experimental phase, ultrasonography was performed to monitor follicular number and diameter, and in the second phase, the animals received LOPU to count the follicles and cumulus-oocyte complexes (COCs) and for morphological classification. There was no significant effect (P > 0.05) of any variable or combination of variables on follicle number on Day (D) 0 or D3/D8 (day of LOPU). However, evaluation at D6/D11 revealed an effect (P < 0.05) from the protocol duration with the highest number of small follicles resulting from the short protocol. There was also an effect (P < 0.05) of FSH dose number on the resulting number of medium and large follicles, with more medium follicles recovered after a single dose and more large follicles after multiple doses. There was no effect of any variable (P > 0.05) on the diameters of the large, medium, and small follicles, except for the D4/D9 evaluation, which showed a combination effect for large follicles (P < 0.05). In the second phase, no variable had an effect on the number of follicles visualized or aspirated, number of COCs recovered, recovery rate, morphological quality of COCs in grades 1, 2, 3, and 4, or rate of viable COCs. Thus, all four protocols efficiently stimulated the ovarian response and oocyte production of goats, although the short protocol (7 days) with a single dose of FSH was most efficacious based upon the greater number of medium-sized follicles available for aspiration, the shorter time, and greater practicality of execution.