Synchronization of Bos indicus × Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2α in combination with melengestrol acetate

• Published in: Journal of animal science 2003, Vol.81 (4), p.830-835
• Main Authors: Hiers, E.A, Barthle, C.R, Dahms, MK.V, Portillo, G.E, Bridges, G.A, Rae, D.O, Thatcher, W.W, Yelich, J.V
• Format: Article
• Language: English
• Subjects: artificial insemination; body condition; breeding season; cows; gonadotropin-releasing hormone; herds; melengestrol; pregnancy rate; prostaglandins; sires; sodium; zebu
• ISSN: 0021-8812; 1525-3163

Nonlactating Bos indicus × Bos taurus cows were used in three herds to determine the efficacy of different PGF2α treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 μg of GnRH. Cows were fed MGA (0.5•mg•cow−1•d−1) on d 1 to 7. On d 7, cows received either a single injection of PGF2α (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 μg; n = 297), or half the recommended dose of PGF2α (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 μg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment × herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment × herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2α treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus × Bos taurus cows.