Effect of follicular ablation and gonadotropin priming on the recovery and quality of oocytes in Boran cows.

Abstract

The objective of the study was to evaluate the effect of follicle ablation, exogenous FSH application, and different coasting time prior to ovum pick-up (OPU) on the number of follicles suitable for aspiration, oocyte quality, and cleavage rate in Ethiopian Boran cows. The experiment was carried out in three parts, (I) cows were synchronized using 500µg PGF2α given 11days apart. Cows were then subjected to a biweekly ovum pickup session before ovulation (n = 5) or starting day 7 after ovulation (n = 4) for 3weeks. (II) Cows were synchronized, and all visible follicles were ablated on the first days of overt estrus, and cows were grouped into those that received a divided dose of 350IU FSH (n = 5) or 175IU FSH (n = 5) over 3days. In both groups, OPU was carried out weekly starting 48h after the last FSH for 6weeks. (III) Protocol was similar to part II, but in group with 350IU FSH (n = 5), coasting period was increased to 72h. The covariates of follicles and oocyte were not affected (P > 0.05) by corpus luteum presence at OPU. The mean number of medium (7.36 ± 0.57) and large (8.28 ± 0.96) follicles were significantly higher (P < 0.05) in the group that received divided 350IU FSH. Similarly, the mean number of grade-1 (4.19 ± 0.24) and grade-2 (4.32 ± .27) oocytes, maturation rate (70.41%), and cleavage rate (47.5%) were significantly higher (P < 0.05) in the group that received 350IU FSH. COC quality was significantly (P < 0.05) influenced by coasting period. However, both maturation and cleavage rates were not affected by the coasting period. This study demonstrated that follicular ablation and treatment with FSH improves follicular population and oocyte recovery rate in Boran cows.