The efficiency of new CIDR and once-used CIDR to synchronize ovulation in primiparous and multiparous Holstein cows

•We evaluate the efficiency of new (N-CIDRsynch) versus reused (U-CIDRsynch) CIDR devices.•Conception and pregnancy rates in the CIDRsynch groups were significantly greater than that in the Ovsynch group.•The U-CIDRsynch regimen achieve satisfactory fertility indices in primiparous Holstein cows.

The objective of this study was to elucidate the efficiency of Ovsynch protocol, new (N-CIDRsynch) and once-used (U-CIDRsynch) controlled internal drug-release (CIDR) devices to synchronize the ovulation time of primiparous and multiparous Holstein cows. The current study was performed on a total of 2207 cows using three different synchronized groups. Conception [pregnancy per AI (P/AI) at day 28] and pregnancy (P/AI at day 75) rates using the N-CIDRsynch and U-CIDRsynch regimens (35.9% and 29.6%; 29.2% and 25.1%, respectively) were significantly greater than those in the Ovsynch group [Odds ratio (OR) = 1.88 and 1.44; 1.92 and 1.52, respectively]. Embryonic loss rate did not differ significantly (P > 0.05) among the Ovsynch, N-CIDRsynch and U-CIDRsynch regimens. In primiparous cows, no significant differences were found in conception and pregnancy rates between the U-CIDRsynch and N-CIDRsynch groups (OR = 0.95 and 1.12; p = 0.693 and 0.451, respectively). In multiparous cows, conception and pregnancy rates in the N-CIDRsynch group were significantly greater than those observed in the U-CIDRsynch group (OR = 0.66 and 0.71; p = 0.016 and 0.027, respectively) and embryonic loss rate in multiparous cows was lower for the U-CIDRsynch treatment than for the N-CIDRsynch treated cows (COR = 0.58; p = 0.048). The present study indicates that the use of a progesterone device in a synchronization protocol may improve fertility in dairy cows compared to the Ovsynch treatment. The use of U-CIDRsynch regimen may achieve satisfactory fertility results compared to those reported with N-CIDRsynch in primiparous Holstein cows.