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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2009-1926v1 87/9/2806    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Filho, O. G. S. Articles by Vasconcelos, J. L. M. PubMed PubMed Citation Articles by Filho, O. G. S. Articles by Vasconcelos, J. L. M.

Strategies to improve fertility in postpartum multiparous Bos indicus cows submitted to a fixed-time insemination protocol with gonadotropin-releasing hormone and prostaglandin F₂¹

O. G. Sá Filho^*, E. R. Vilela^*, T. W. Geary and J. L. M. Vasconcelos^*,2

^* Departamento de Produção Animal, Faculdade de Medicina Veterinária e Zootecnia-UNESP, P 18618-000, Brazil; and USDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT 59301

² Corresponding author: vasconcelos{at}fca.unesp.br

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 PGF₂ followed by another injection of GnRH and fixed-time AI (TAI) 2 d after PGF₂], with or without temporary weaning (TW) before GnRH treatments, on fertility of suckled multiparous Bos indicus cows (n = 283) and on calf performance. Timed AI 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 PGF₂ 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 PGF₂ 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 TAI 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.

Key Words: anestrous • Bos indicus • gonadotropin-releasing hormone • progesterone-releasing intravaginal insert • prostaglandin F₂ • timed artificial insemination