Influence of antral follicle count on in vitro embryo production, sexual precocity and conception rate of Senepol cattle

Abstract

Context There are contradictory results concerning the relationship between antral follicle count (AFC) and reproductive traits for different breeds of cattle. Understanding this relationship could be useful to selecting animals for breeding. Aims We evaluated the effects of AFC on parameters related to in vitro embryo production (IVP), and the influence of AFC on sexual precocity and conception rate at first fixed timed artificial insemination (FTAI) of Senepol females. Methods Ovarian ultrasound was performed to count antral follicles, and females were classified as low AFC (≤22 follicles), intermediate AFC (23–36 follicles) or high AFC (>36 follicles). Expt 1 evaluated the influence of AFC on IVP, with data from 146 adult cows that were submitted to follicular aspiration. Expt 2 evaluated the influence of AFC on heifer sexual precocity, determined by the presence of a corpus luteum (n = 608), and on conception rate at first FTAI (n = 143). Key results High AFC cows had a greater (P < 0.0001) number of viable oocytes and cleaved embryos and a higher average number of embryos than low AFC cows (38.28 vs 9.92, 38.28 vs 7.75 and 9.34 vs 2.41, respectively). However, the conversion rate (total viable embryos per oocytes) was not affected (P = 0.46) by AFC category. High AFC heifers tended (P = 0.07) to be more sexually precocious than low AFC heifers (16.73% vs 9.47%). An influence of AFC or of AFC category on conception rate at first FTAI was not detected (P = 0.35 and 0.19, respectively). Conclusions Despite greater IVP in high AFC cows, the conversion rate of viable oocytes to IVP was not affected by AFC category. High AFC heifers tended to be more sexually precocious, although AFC did not influence the conception rate at first FTAI. Implications Oocyte quality is probably not influenced by AFC, but selection of animals according to AFC may improve the sexual precocity of the herd.