Efficacy of three synchronization protocols on the pregnancy rate in lactating dairy crossbred cows after fixed time artificial insemination

Abstract

Background and Objective: Ineffective estrus detection is the foremost limiting factor in the fertility of farmed cattle worldwide. Therefore, this study investigates the effect of three synchronization protocols with Fixed Time Artificial Insemination (FTAI) on the pregnancy rate of crossbred dairy cows. Methodology: Ninety one cows were assigned to four groups where the Body Condition Score (BCS), age distribution, parity and average daily milk yield were apparently even among groups then each group received 1 of 4 treatments: (1) Ovsynch-CIDR treated cows (n = 24) received 10 μg gonadotropin releasing hormone (GnRH, IM, Buserelin acetate) with insertion of Controlled Internal Drug Release device (CIDR) on day 0 followed by 500 μg prostaglandin F2α (PGF2α, IM, cloprostenol sodium) and CIDR removal on day 7. On day 9, cows received the second dose (10 μg) of GnRH followed by FTAI 18 h later, (2) PGF2α-synchronized cows (n = 25) received double doses of 500 μg PGF2α analogue (cloprostenol sodium) 12 days apart followed by FTAI 80 h after the second dose of PGF2α, (3) Ovsynch treatment (n = 17) with 10 μg GnRH-day 0, 500 μg PGF2α-day 7 and 10 μg GnRH-day 9 sequence followed by FTAI 18 h later and (4) Untreated cows (control, n = 25). Blood samples were taken for progesterone (P4) determination on days 0, 7 and on day of AI. Results: Our results revealed that pregnancy rate was greater (p<0.05) in PGF2α (36%), compared with ovsynch (29.4%), ovsynch-CIDR (20.8%) and control (12%) cows. Conclusion: In conclusion, acceptable pregnancy rates can be achieved with FTAI after 80 h of synchronized cows with double doses of PGF2α 12 days apart compared with synchronization of ovulation with (ovsynch-CIDR) or without (ovsynch) P4 supplementation.