Estradiol and GNRH on Ovulation Induction for Estrus Synchronized Crossbred Cows1

Abstract

Estradiol benzoate (EB), estradiol cypionate (EC), and gonadotrophin releasing hormone (GnRH) were evaluated as ovulation inducers for TAI of crossbred lactating cows. In experiment I (n = 45), the follicular dynamics was evaluated, while in experiment II (n = 171) the reproductive efficiency was evaluated. All females were submitted to a synchronization protocol: insertion on day 0 (D0) of intravaginal progesterone -release intravaginal device (PRID; 1g) plus administration of EB 2mg; D8, PRID removal, administration of 0.150mg PGF2α and 400 IU of eCG, and cows were allocated into three treatments: 1) TEB9 - IM administration of 1mg EB on D9 and AI performed 52 hours after PRID removal; 2) TEC - IM administration of 1mg EC on D8 and AI performed 48 hours after withdrawal of PRID; and 3) TGnRH - administration of 100pg GnRH on D10 and AI performed 52 hours after removal of PRID. The follicular growth rate was lower in the EC group (p <0.05). There was no effect of treatments on ovulation and pregnancy rates (p >0.05). The use of EB, EC, and GnRH as ovulation inducers in the TAI protocol did not show marked differences in the evaluated patterns of follicular dynamics and pregnancy.

Performance and Cost-Efficiency of Single Hormonal Treatment Protocols in Tropical Anestrous Dairy Cows

“…Some farmers question the value of hormone treatment due to its higher cost than estrus detection followed by AI alone. The use of reproductive hormones, synchronization programs, and TAI in anestrous bovine species (cows and buffaloes) in tropical countries has been studied and showed desired results in improving reproductive performance under tropical conditions [ 11 , 18 , 19 , 20 , 21 , 22 ]; however, information on the cost-efficiency of different hormonal treatment protocols is still limited.…”