ABSTRACT
A study on postpartum dairy cows was done to evaluate the effect of using progesterone intravaginal device (CIDR) to synchronize return to oestrus of previously timed inseminated (TAI) cows and to evaluate embryo survival and pregnancy rate in the return to oestrus cows. All cows were subjected to TAI program. On Day 14 after AI, cows were assigned randomly into two groups: treated group (CTAI; n=126) and control group (TAI; n=172). Every cow in the CTAI group received CIDR device for 7 days. Cows were observed for oestrus after CIDR removal in the first period (Days 21-28). Cows, which did not show oestrus, were retreated with CIDR on Day 28 for 7 days and they were observed for oestrus after CIDR removal in the second period (Days 35-42). Pregnancy was diagnosed on Days 28, 45 and 90 after AI. In the first period, more cows in the CTAI group showed oestrus within 2.4 days after CIDR removal compared to cows within 4 days in the control. In the second period, more cows in the CTAI group showed oestrus within 4.5 days compared to cows within 3.7 days in the control. Pregnancy rates on Day 28 were not different between both groups. Pregnancy rates on Days 45 and 90 were higher for cows in the CTAI (42.1+/-5.3%, P=0.028 and 38.9+/-5.2%, P=0.020) compared to that in the TAI group (35.5+/-3.9% and 31.9+/-3.8%). Moreover, pregnancy rates were lower for multiparous cows (34.2+/-4.1, P=0.017 and 30.2+/-3.9%, P=0.008) compared to primiparous cows (42.7+/-5.2% and 39.9+/-5.1%) on Days 45 and 90, respectively. Pregnancy losses between Days 28-45 and 45-90 tended to be lower for the CTAI group and primiparous cows compared to the TAI group and multiparous cows. Pregnancy rates of first (P=0.020), second, third and up to fourth AI were higher (P=0.001) for the CTAI group (38.9+/-0.05%, 78.6+/-0.05%, 92.1+/-0.04%, 93.6+/-3.71%) compared to that for the TAI group (31.9+/-0.03%, 54.1+/-0.04%, 68.0+/-0.03%, 81.4+/-2.75%, respectively). Days open for pregnant cows were similar in both groups, but lower (P=0.025) for primiparous cows (81.6+/-4 day) compared to multiparous cows (93.8+/-3 day). Number of services for pregnant cows was lower (P=0.002) for the CTAI group (1.70+/-0.10) compared to that for the TAI group (2.14+/-0.09), whereas it was similar for primiparous and multiparous cows. Results indicate that the CIDR device improved synchronization to return to oestrus and increased pregnancy rate to first, second, third and fourth AI by reducing embryonic and fetal losses.
