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

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(2alpha)) 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(2alpha) injection and then by another GnRH injection 9 days later. Artificial insemination (AI) was performed 16 h after the second GnRH injection. Injections of PGF2 were given 11 days apart AI was only carried out after estrus was detected following the first and second PGF(2alpha) injections or, timed AI in the absence of detected estrus was carried out 72 h after the second PGF(2alpha) injection. The conception rate in first insemination, pregnancy rate and the interval from PGF(2alpha) 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(2alpha)-GnRH method allowed effective management of AI in cows and heifers without the need for estrus detection.