2011 Volume 64 Issue 11 Pages 870-873
The effect of CIDR inclusion for seven days after timed artificial insemination (TAI) on reproductive performance was determined in Japanese Black cows. Ovulation was synchronized at one month after normal parturition and was subjected to TAI. Cows were divided into two groups with CIDR inclusion for 7 days at 17 days after TAI (n ＝28) or controls without CIDR (n ＝47). Conception rates with TAI were similar (CIDR 64.3% vs. controls 53.2%, P ＝0.42). The date of return of estrus in open cows were similar (CIDR 28.7 ± 3.9 days vs. control 33.0 ± 26.9 days, P ＝0.22), however there was heteroscedasticty in these groups (P ＜0.01), and the coefficient of variation in CIDR was smaller than in the control. The conception rates of re-AI in open cows both within 7 days after CIDR removal in CIDR and from 18 days to 24 days after TAI in controls were similar. (CIDR 85.7% vs. control 68.3%, P ＝0.47). The inclusion of CIDR for 7 days at 17 days after TAI reduced the dispersion for the timing of the return of estrus in early postpartum Japanese Black cows.
