Effects of ovarian follicular status on superovulatory response of dairy goats to FSH treatment

This study evaluates the response of Murciano-Granadina goats to superovulatory FSH treatments, in terms of number of corpora lutea (CL) and transferable embryos, as well as the variability between replicates and the possible effects of follicular status on superovulatory yields. A total of 169 goats were allocated to nine different groups, and treated with 45 mg fluorogestone acetate (FGA) sponges for 16 days plus a single dose of 100 μg i.m., cloprostenol on Day 14. The superovulatory treatment in all groups consisted of eight doses of 1.25 ml of Ovagen™, twice daily from 60 h before to 24 h after the removal of the progestagen treatment. In the animals from the last three groups (50 females), all follicles ≥2 mm were evaluated by transrectal ultrasonography at the time of the first FSH injection. The response to the FSH treatment, in all the goats, was 14.3+/-0.5 corpora lutea, 11.3+/-0.5 recovered embryos (RE) and 6.8+/-0.4 viable embryos (VE) per goat. Superovulatory yields varied widely between replicates, with significant differences in number of corpora lutea (P<0.01), recovered embryos (P<0.05) and viable embryos (P<0.01). This variability in response to the superovulatory protocol is related with follicular status of the donor at the beginning of the treatment. The number of corpora lutea was positively correlated with the total number of follicles with a diameter of 2-6 mm (P<0.05; r=0.826). However, the number of recovered and viable embryos were related to the more limited category of follicles of 4-6 mm in size (6.2+/-0.5), which could indicate that oocytes from smaller follicles are not fully mature. Current results indicate that ultrasonography can be used as a practical criteria for selection of donor goats, which could avoid the treatment of poor-responding females, and provide a basis for the study of suitable treatments to make ovarian follicular populations uniform.