The effects of intramuscular or intravenous injections of gonadotropin releasing hormone at fixed-time artificial insemination on pregnancy rates of Bos indicus beef cows

Autor: Danilo Demeterco, Darren Dwayne Henry, Vitor Rodrigues Gomes Mercadante, Graham Cliff Lamb, Francisco Romano Gaievski, Bruno Weiss, Gustavo Nascimento Turbay, Márcio Saporski Segui, Romildo Romualdo Weiss, Melina Andreia Formighieri Betiol, Luiz Ernandes Kozicki
Jazyk: angličtina
Rok vydání: 2014
Předmět:
Zdroj: Brazilian Archives of Biology and Technology, Vol 57, Iss 3, Pp 361-366 (2014)
Druh dokumentu: article
ISSN: 1678-4324
1516-8913
DOI: 10.1590/S1516-89132014000300008
Popis: The effect of an intramuscular versus intravenous administration of gonadotropin releasing hormone (GnRH) at fixed-time AI (FTAI) on the pregnancy rates of crossbred Bos indicus beef cows was evaluated. Pluriparous nursing calv cows (n=120) were synchronized as follows: d 0 cows received a 2.0 mg injection of estradiol benzoate (EB) and insertion of a controlled intravaginal progesterone releasing device containing 0.558 g of progesterone, d 8 removal of the progesterone device , a 0.15 mg injection of prostaglandin F2α (PGF), a 1.0 mg injection of EB, and 400 IU injection of equine chorionic gonadotropin. Fifty-four hr after PGF, all cows were exposed to FTAI and a 0.084 mg injection of GnRH was administered either via Vena caudalis (n=60), or via Longissimus dorsi (n=60). Cows were inseminated with the same sire and by a single AI technician. Pregnancy was determined by the transrectal ultrasonography on d 40 after AI. Cows receiving the intravenous administration of GnRH had higher (P = 0.04) pregnancy rates than the cows receiving the intramuscular injection of GnRH (65 vs 46.6%, respectively). It was concluded that the intravenous administration of GnRH at the time of AI improved the pregnancy rates of crossbred Bos indicus beef cows submitted to FTAI.
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