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- Title
Strategies to improve fertility in postpartum multiparous Bos indicus cows submitted to a fixed-time insemination protocol with gonadotropin-releasing hormone and prostaglandin F<sub>2α</sub>.
- Authors
Sá Filho, O. G.; Vilela, E. R.; Geary, T. W.; Vasconcelos, J. L. M.
- Abstract
In Exp. 1, we evaluated the effects of 2 lengths of progesterone exposure [CIDR (controlled intravaginal drug release); 7 vs. 14 d] before a modified CO-Synch protocol [50.0-μg injection of GnRH 6.5 d before a 25.0-mg injection of PGF2α followed by another injection of GnRH and fixed-time AI (TAI) 2 d after PGF2α], with or without temporary weaning (TW) before GnRH treatments, on fertility of suckled multiparous Bos indicus cows (n = 283) and on calf performance. Timed AT pregnancy rates for cows receiving 7 d CIDR + TW, 7 d CIDR, 14 d CIDR + TW, and 14 d CIDR were 53, 47, 46, and 41%, respectively (P > 0.10). Calves submitted to two 48-h TW 6 d apart had decreased mean BW at 240 d (187.9 ± 2.7 vs. 195.5 ± 2.7 kg; P < 0.05), but BW at 420 d was not affected by TW (240.1 ± 5.1 kg). In Exp. 2, we evaluated the effect of no treatment and treatment with or without a CIDR insert between GnRH and PGF2α treatments of a modified CO-Synch protocol on pregnancy rate to TAI, and throughout a 90-d breeding season in suckled multiparous Bos indicus cows (n = 453). The inclusion of a CIDR between first GnRH and PGF2α treatments of a modified CO-Synch protocol did not improve pregnancy rate (29 and 33% for cows receiving CO-Synch + CIDR and CO-Synch protocol, respectively), and cycling cows had poorer TAT pregnancy rates than anestrous cows treated with either synchronization protocol (21.7 vs. 40.7%; P < 0.05). However, regardless of treatment with CIDR, cows submitted to TAI protocol had greater (P < 0.05) pregnancy rates at 30 (54.8 vs. 11.2%), 60 (72.1 vs. 38.8%), and 90 d (82.0 vs. 57.9%) of breeding season than untreated cows.
- Subjects
COWS; FEMALE livestock; ANIMAL genetics; LIVESTOCK genetics; CATTLE parturition; ARTIFICIAL insemination of cattle; ANIMAL breeding; GONADOTROPIN
- Publication
Journal of Animal Science, 2009, Vol 87, Issue 9, p2806
- ISSN
0021-8812
- Publication type
Article
- DOI
10.2527/jas.2009-1926