Comparison between 7 vs 9 days of controlled internal drug release inserts permanency on oestrus performance and fertility in lactating dairy cattle

摘要

The objective was to evaluate the reproductive performance after oestrus synchronization using controlled internal drug release (CIDR) maintained into the vagina either 7 or 9 days. A controlled randomized block design was performed. Cows (n=255) wereblocked by lactation number and days in milk and then randomly divided into 2 groups. In the first group, CIDR was maintained for 7 days (CIDR-7; n=127), and in the second group, CIDR was maintained for 9 days (CIDR-9; n=128). Both groups received Prostaglandin-F2α at CIDR removal. Oestrus response, oestrus onset, oestrus duration, conception rate, and pregnancy at days 28 and 45 were evaluated. Cows were oestrus detected 4 times a day for 120 hours after CIDR removal, and only cows in standing oestrus were artificially inseminated between 6 and 12 hours after oestrus detection. Oestrus response for both groups was 79.5% and 87.5% for CIDR-7 and CIDR-9, respectively (P=0.09). The oestrus onset (mean ± SD) for the same groups was 56.3±17.2 h and 59.4±17.9 h, respectively (P=0.19). Oestrus duration was 11.3±7.3 h and 11.7±7.8 h for groups CIDR-7 and CIDR-9, respectively (P=0.71). At day 28, the conception rates for the groups CIDR-7 and CIDR-9 days were 51.5% and 45.5% (P=0.39), and the pregnancyrates were 40.9% and 39.8% (P=0.89) for the same groups, respectively. No differences in oestrus performance and fertility in lactating cows’ oestrus synchronized by using CIDR maintained in the vagina either 7 or 9 days were detected.