Timed artificial insemination (TAI) based on CIDR first, second or third use in Bos indicus cows

Abstract

The study aimed to verify the effects of CIDR (P4) first, second or third use on PR in protocols for TAI. Five hundred and forty-seven Nelore cows were divided: CIDR1 (CIDR first use; n=196); CIDR2 (second use; n=188) and CIDR3 (third use; n=163). All animals were submitted to the same protocol: day 0(d0), 2mg EB+CIDR1, CIDR2 or CIDR3, according the CIDR use; d9, CIDR removal + 12.5 dinoprost thrometamin+0.6mg ECP + 48 hours calf removal; d11, TAI + return of the calves to dams. The overall pregnancy rate (PR) was 63.8, 53.7 and 27.0% for CIDR1, CIDR2, and CIDR3, respectively. Differences in the PR were observed between: CIDR1 and CIDR2 (P=0.04); CIDR1 and CIDR3 (P=0.0001); and CIDR2 and CIDR3 (P=0.0001). The open days (OD) in post partum and body condition score (BCS) resulted in differences (P<0.05) among groups. There was a correlation between open days in CIDR 1 and 2 versus BCS, as well as between BCS of the CIDR 1 and 3 against PR In conclusion, CIDR1 showed better reproductive efficiency than CIDR2 and CIDR3 use. Differences were observed between the groups in regard to DO, and by cows submitted to CIDR earlier in the postpartum period having a lower PR than those submitted at a later time. A BCS of 3.1 resulted in a higher PR than those with 3.5 and 3.7.