Effect of a single prostaglandin F2α presynchrony 3 to 4 days prior to treatment of anestrous dairy cows with a novel intravaginal progesterone-releasing device and Ovsynch

This randomized positively controlled intervention study assessed the superiority of presynchrony by a single i.m. injection of PGF_2α given 3 or 4 d before commencement of an Ovsynch and progesterone program, compared with no presynchrony, in anestrous cows. Additionally, noninferiority of a novel intravaginal progesterone-releasing device (Ulti-mate) compared with a commercially available device (CIDR) was assessed. Cows (n = 1,557) not detected in estrus by 12 or 13 d before the start of the seasonal breeding program (d 0) and calved >13 d, were blocked within herd by lactation (i.e., primiparous vs. multiparous) and randomly assigned to treatment with Ulti-mate or CIDR devices, and presynchrony or not, in a 2 × 2 factorial design. At d -12 or -13 cows assigned to presynchrony received an i.m. injection of PGF_2α. On d -9 all cows received GnRH and the assigned device. On d -2 the devices were removed, and all cows received PGF_2α at device removal and again 24 h later. Cows not observed in estrus by ∼56 h after device removal were injected with GnRH and bred ∼16 h later. Those cows that had been detected in estrus by the time of the final GnRH were not injected. A subset of 128 cows from 2 herds underwent ovarian ultrasonography on d -12, -9, -7, -1 and +2, and blood samples were drawn from the tail vessels on d -12, -9, and -7 for serum progesterone analyses. Pregnancy status was determined by transrectal ultrasonography at ∼5 wk after first insemination, and again ∼6 wk after the end of the seasonal breeding program. Pregnancy per artificial insemination (AI) was greater in presynchronized (54.3%, 95% CI: 50.4%-58.2%) than non-presynchronized (49.2%, 95% CI: 45.2%-53.1%) cows. Presynchrony also resulted in greater proportions of cows pregnant by 3 and 6 wk into the breeding program. There were 71/128 cows with corpora lutea detected by ultrasonography at d -12. Presynchrony increased the proportion of these cows undergoing luteolysis between d -12 and d -9 compared with no presynchrony (23/28 [82.1%] vs. 11/29 [37.0%]). Neither device type nor presynchrony altered the proportion of cows ovulating following device removal by d +2. There was no difference in pregnancy per AI or the proportion of cows pregnant by 3 or 6 wk between cows treated with Ulti-mate or CIDR devices The Ulti-mate device was declared noninferior to the CIDR device in terms of pregnancy per AI because the lower 95% CI of the difference was less than -7 percentage points. We conclude that presynchrony with PGF_2α, 3 or 4 d before progesterone-releasing device insertion, resulted in greater pregnancy per AI and greater pregnancy proportion by 3 and 6 wk into the breeding program.