The purpose of this study was to see how the Ovsynch, modified Ovsynch, presynch, and modified presynch protocols affected postpartum reproductive performance in dairy cows. Design: Randomized controlled experimental study Animals: The current research involved 412 dairy cows. Procedures: The cows were split into four groups: GnRH was given on day 0, PGF2∝ on day 7, and GnRH on day 9. Group 1: (Ovsynch protocol, n= 117) received GnRH on day 0 and PGF2∝ on day 7. Group 2 (modified Ovsynch, n=113): PMSG on day 0, PGF2 on day 7, and PMSG on day 9. Group 3 (presynch protocol, n=98) got two doses of PGF2 14 days apart, which allowed for a 12-day delay in the start of Ovsynch. Group 4 (modified presynch protocol, n=84) got two PGF2∝ doses 14 days apart, which was 12 days before the start of modified Ovsynch. All of the animals were artificially inseminated 16 hours following their last GnRH or PMSG dose. The ovarian rebound, number of services per conception, days open, and calving interval were the measures for determining reproductive performance for the dairy cows. Results:The main effect of the synchronisation program showed no significance for ovarian rebound (P >0.05). The S/C, days open and calving intervals were decreased significantly (P＜0.05) in the 3rd and 4th groups when compared with the cows that received either GPG or PMSG treatment only. All four groups had a conception rate of 35.04 (41/117), 40.7 (46/113), 44.8 (44/98), and 57.14 (48/84) %, respectively (P＜0.05). Conclusion and clinical relevance:It was investigated that giving two PGF2 injections before Ovsynch, either utilizing GnRH or PMSG methods, improved the reproductive performance of dairy cows. Furthermore, cows given PMSG had a greater conception rate than cows given GnRH.

This review focused on the various methods for controlling estrous cycles in well-managed dairy cows. Because up to 70% of dairy cows may stay non-pregnant after an AI procedure, an effective approach for identifying and reinseminating open cows is essential for dairy herds to achieve optimal reproductive performance. Overall, well-managed dairy farms with effective estrus detection programs inseminate 50% or more of non-pregnant cows after behavioral estrus is detected. Cows not detected in estrus are admitted in a resynchronization of ovulation procedure to receive a timed AI (TAI) service to avoid a long interbreeding interval. In Egypt, a widely used program involves starting the Ovsynch protocol (GnRH-7 d-PGF2-56 h-GnRH-16 to 20 h-TAI) 32 days after an initial AI, regardless of pregnancy status. Previous studies have proven that there was no difference in pregnancy/artificial insemination (P/AI) between Ovsynch+P4 and Presynch-Ovsynch, both protocols were equally effective in improving the fertility of cows with a CL 15 mm. The review also addressed different methods for synchronization of ovulation and different factors affecting the selection of the management program.

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