Reproductive Performance and Synchronization of the Ovulation and Estrus in Brown Swiss Cows and Heifers Using the Protocol GnRH- PGF2 alpha-GnRH and PGF2 alpha


Abstract: The objective was to compare the reproductive performances of Brown Swiss cows and heifers synchronized for estrus and ovulation using prostaglandin F 2 alpha (PGF_{2\alpha}) alone or with gonadotropin-releasing hormone (GnRH). Primiparous and multiparous cows (45 to 75 days postpartum; n = 26) and nulliparous heifers (16 to 20 months; n = 26) were randomly assigned to 2 treatment programs. GnRH injection was followed in 7 days by PGF_{2\alpha} injection and then by another GnRH injection 9 days later. Artificial insemination (AI) was performed 16 h after the second GnRH injection. Injections of PGF_{2\alpha} were given 11 days apart AI was only carried out after estrus was detected following the first and second PGF_{2\alpha} injections or, timed AI in the absence of detected estrus was carried out 72 h after the second PGF_{2\alpha} injection. The conception rate in first insemination, pregnancy rate and the interval from PGF_{2\alpha} to estrus were not different between the 2 groups. However, the estrus detection rate was greater for the group II cows (61.5%) than for the group I cows (15.4%) (P < 0.05). Pregnancy rates tended to be higher in group I cows. The GnRH-PGF_{2\alpha} -GnRH method allowed effective management of AI in cows and heifers without the need for estrus detection.

Keywords: Dairy cattle, synchronization of estrus, synchronization of ovulation, gonadotropin-releasing hormone, prostaglandin F_{2\alpha}

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