The role of pre-ovulatory progesterone concentrations on conceptus development, endometrial transcriptome, and fertility in dairy cows.

摘要

Objectives were to evaluate the effects of manipulating progesterone concentrations in plasma during the development of the ovulatory follicle on fertility responses in dairy cows. In the first study, supplementing progesterone using a single intravaginal insert did not improve pregnancy per artificial insemination (P/AI) in lactating dairy cows with corpus luteum (CL). Results from the meta-analysis indicate that incorporating a single intravaginal insert containing progesterone to the timed AI program increased P/AI and tended to reduce pregnancy loss in lactating dairy cows independently of the presence of CL. However, the benefit of progesterone supplementation on P/AI was eliminated if cows were observed for signs of estrus during the synchronization protocol and had the opportunity to be inseminated before timed AI. Increasing the concentration of progesterone in plasma using two intravaginal inserts restored P/AI in lactating dairy cows without a CL at the initiation of the timed AI program similar to that of cows in diestrus in the third and fourth studies. The mechanisms that underlie the effects of progesterone during the growth of the ovulatory follicle were evaluated in the fifth study. Non-lactating dairy cows were induced to ovulate the dominant follicle from the first (FW) or second wave (SW) of the estrous cycle at AI (naturally occurring low and high progesterone concentrations, respectively). A third group of cows received progesterone supplementation using three intravaginal inserts during the first follicular wave (FWP4). The diameter of the ovulatory follicle and concentrations of estradiol in plasma preceding ovulation were greater for FW compared with FWP4 and SW. Progesterone concentrations after ovulation were greater for FW compared with FWP4 and SW, which was associated with greater CL volume and weight. Conceptuses recovered on day 17 after AI were longer for FW compared with FWP4 and SW. Nevertheless, concentrations of interferon-tau (IFN-tau) in the recovered uterine flush, the transcriptome of the endometrium in pregnant cows, and the respective conceptuses were not extensively affected by follicular wave or concentrations of progesterone during follicle growth. In conclusion, increasing the concentrations of progesterone during growth of the ovulatory follicle improved fertility in dairy cows.