Application of one injection of prostaglandin F_(2α) in the five-day Co-Synch + CIDR protocol for estrous synchronization and resynchronization of dairy heifers

摘要

The objective was to determine if the 5-d Co-Synch + CIDR (controlled internal drug releasing insert) protocol can be used in dairy heifers for a synchronized timed artificial insemination (TAI) with one injection of PGF_(2α) for first and second services. In experiment 1, heifers were assigned randomly to receive 1 (n = 295) or 2 (n = 298) injections of PGF_(2α) in the 5-d Co-Synch + CIDR protocol. Corpus luteum (CL) regression was measured in one replicate (n = 218). No difference in pregnancy per TAI (P/TAI; 46.1 and 48.6%) or CL regression (86.9 and 92.8%) was detected for 1 versus 2 injections of PGF_(2α), respectively. In experiment 2, nonpregnant heifers (n = 86) were assigned to a re-synchronized 5-d Co-Synch + CIDR with 1 PGF_(2α)/ TAI or insemination at detected estrus. There was no difference in P/TAI (52.2 and 55%) between groups. In experiment 3, nonpregnant heifers (n = 110) were assigned randomly to receive a CIDR (n = 54) or no CIDR insert (n = 56) in the 5-d Co-Synch protocol for resynchronization of TAI. Pregnancy per TAI was lower without the CIDR device (39.3 vs. 51.8%). In a commercial field evaluation, 416 heifers were synchronized for the first and resynchronized TAI with the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_(2α). Pregnancy per TAI on d 60 was 58.2 and 47.5% for first and second TAI, respectively; there was a sire effect to the second TAI. In conclusion, the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_(2α) is an effective reproductive management program for first and second TAI in dairy heifers.