Estrous Synchronization Using PGF2 with GnRH or Estradiol Benzoate to Improve Reproductive Performance of Lactating Dairy Cows

Mufeed A. Alnimer


Lactating dairy cows (n= 470) were used to evaluate the effect of two estrous synchronization protocols starting on d 10 of the estrous cycle on reproductive performance. OVS: Gonadotropin Releasing Hormone (GnRH)-Prostaglandin F2a (PGF2a)-GnRH and timed Artificial Insemination (TAI) and EPG: Estradiol Benzoate (EB)-PGF2a and GnRH and TAI. Pregnancy rates on d 45 and 90 were greater for the OVS (43.0%, P = 0.004 and 41.1%, P = 0.002) compared to the EPG group (30.2% and 27.4%) and were lower for multiparous cows (29.9%, P = 0.008 and 27.2%, P = 0.004) compared to primiparous cows (42.0% and 39.9 %), respectively. Pregnancy rates to first AI (P = 0.002), and overall AI were greater (P = 0.001) for the OVS (40.7% and 97.7%) compared to the EPG group (26.9% and 89.6%; respectively). Moreover, pregnancy rates of first, second, third and overall AI were lower (P = 0.001) for multiparous cows (26.6, 57.6, 77.7 and 90.2%, respectively) compared to primiparous cows (39.5, 71.3, 89.2 and 96%, respectively). Days open and the number of services per pregnancy were lower (P = 0.014; P = 0.001) for the OVS (81.7 d and 2.01) compared to the EPG group (88.5 d and 2.14) and lower (P = 0.001) for primiparous (80.6 d and 1.94) compared to multiparous cows (89.6 d and 2.22). Results indicate that a significant improvement in reproductive performance of timed AI cows following OVS than EPG program as measured by pregnancy rate, days open and number of services per pregnancy. In addition, primiparous cows had better reproductive performance than multiparous cows.

الكلمات المفتاحية

Dairy Cows, Estrous-Synchronization, GnRH, Estradiol, TAI, Reproductive Performance.

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