Follicular development and superovulation response in cows administered multiple FSH injections early in the estrous cycle

To determine whether follicular development, superovulation and embryo production were affected by the absence or presence of a dominant follicle, cows were administered injections of FSH twice daily in the early (Days 2 to 6, estrus = Day 0) or middle stage (beginning on Day 10 or 11) of the estrous cycle. Treatment with FSH early in the cycle stimulated follicular development in 83 to 100% of all cows from 4 groups evaluated at different times after PGF2α treatment on Days 6 and 7. However, the proportion of cows with > 2 ovulations varied from 31 to 62.5%, indicating that induction of follicular development may occur in the absence of superovulation. When compared with cows treated in the middle of the cycle, no differences were observed in the proportion of cows with > 2 ovulations (31 vs 20%), ovulation rate. (26.0 ± 6.3 vs 49.6 ± 25.8), production of ova/embryos (13.3 ± 3.2 vs 14.4 ± 3.4), or the number of transferable embryos (8.0 ± 3.6 vs 5.4 ± 1.5; early vs middle, respectively). The proportion of the total number of embryos collected that were suitable for transfer was greater (P