Abstract
Background:
Reproductive efficiency affects dairy cow profitability. Ovarian function in postpartum has been better understood using ultrasound and hormonal assays. Optimizing ovulation synchronization and carefully timing artificial insemination can greatly enhance reproductive rates in dairy cows.
Aim:
This experiment was designed to investigate the reproductive performance and ovarian activity in early postpartum lactating dairy cows using the Presynch-PGF2α, Ovsynch protocol and timing artificial insemination (TAI).
Methods:
Randomly the cows were assigned to a control group and a treatment group, based on chronological order of their calving date. On Day 14 postpartum (P.P), both groups received two cloprostenol treatments, 14 days apart. Ultrasonographic inspections were conducted on day 14 to check ovarian activity and uterine contents. On day 11 after presynchronization, cows in the treatment group were given 100 µg im. of cystorelin, followed by a luteolytic dose of 500 µg IM. cloprostenol on day 7 and a second dose of cystorelin on day 8 (36 hours later). After the second cystorelin injection by16-20 hrs., cows were inseminated, while the control group had all cows displaying spontaneous estrus between day 0 and day 28 was artificially inseminated.
Results:
Ovarian activity began to improve at 82.61% on day 19 P.P., with complete recovery between days 24 and 27 P.P. The second cloprostenol injection approached, causing follicular size to reach 8.41±1.04 mm. After the second injection, ovarian activity switched from follicular to luteal, with corpus luteum (CL) rates of 23.91 and 26.1%. The presynchronized PGF2α regimen significantly enhanced ovarian activity from days 19–35 P.P. Ovulation and pregnancy rates in the Ovsynch group were 54.2% and 41.7% at the first timed artificial insemination (TAI), compared to 54.5% and 31.8% in the control group. There was no significant impact between them; it was just high in the presynchronized Ovsynch group. But the postpartum period was minimized to 47–49 days till the first AI to reach a 41.7% pregnancy rate and 20.8% at the second AI, for an overall 62.5%.
Conclusion:
The current study concludes that presynchronization during preservice in clinically normal postpartum dairy cows reduces postpartum duration, increases ovarian activity performance, and reduces ovarian dysfunctions from Day 19 to Day 35 postpartum, as well as improve the pregnancy rate.

Key words: Postpartum cow, Ovarian activity, Presynchronization, Ovsynch, TAI