Abstract
This investigation was carried out on privately owned dairy farms situated in Al-Anbar Province, Iraq, extending from June 2022 to March 2023. The objective of our study was to compare the calving interval (CI), days open (DO), and conception rate at first service (CRFS) between timed artificial insemination (TAI) within ovulation synchronization protocols and AI at estrus detection. Total cows (n = 80) 50–60 days postpartum were randomly divided. (1) AIED group (Control, n = 40) untreated cows received AI at the first observed estrus according to the a.m. /p.m. rule. (2) OVS group (n = 20) was treated with a classical Ovsynch protocol. (3) The PG+G group (n = 20) underwent resynchronization with PGF2 and GnRH at the same time 7 days later, then underwent an Ovsynch protocol. Pregnancy was confirmed using trans-rectal ultrasonography on day’s 30-35 post-insemination. The results of this study show that mean days of CI and DO for the control group were significantly longer than those in both the OVS group and the PG+G group (P < 0.01). Among all groups, the CRFS showed a significant difference (37.5%, P < 0.05). Separately, the CRFS for the control group was similar to the OVS group (respectively, 27.5% vs. 30%, P > 0.05). Whereas, the PG+G group had a 65% CRFS, which was significantly higher than the control (P < 0.01) and OVS (P < 0.05). In summary, ovulation synchronization protocols enable TAI earlier in the postpartum period, eliminating the need for estrus detection and resulting in shorter CI and DO. Additionally, the PG+G protocol increased the CRFS compared to both the OVS and the control groups.

Key words: Conception Rate, Dairy Fertility, Ovsynch. Timed AI.