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.

摘要：本研究评估了苯甲酸雌二醇（Estradiol benzoate, EB）、环戊丙酸雌二醇（estradiol cypionate, EC）及促性腺激素释放激素（gonadotrophin releasing hormone, GnRH）作为排卵诱导剂，用于杂交泌乳奶牛的定时人工授精（TAI）效果。实验一（n=45）旨在评估卵泡动态变化，实验二（n=171）则评估繁殖效率。所有受试母牛均采用同期发情同步方案：于第0天（D0）放置阴道内孕酮释放装置（PRID；1g）并肌肉注射2mg苯甲酸雌二醇；第8天（D8）移除PRID，注射0.150mg前列腺素F2α（PGF2α）与400 IU孕马血清促性腺激素（eCG），随后将母牛分为3个处理组：1）TEB9组：于D9肌肉注射1mg苯甲酸雌二醇，在PRID移除后52小时开展人工授精；2）TEC组：于D8肌肉注射1mg环戊丙酸雌二醇，在PRID移除后48小时开展人工授精；3）TGnRH组：于D10注射100pg促性腺激素释放激素，在PRID移除后52小时开展人工授精。结果显示，环戊丙酸雌二醇组的卵泡生长速率显著偏低（p<0.05）。各处理组对排卵率与妊娠率均无显著影响（p>0.05）。在定时人工授精方案中使用苯甲酸雌二醇、环戊丙酸雌二醇及促性腺激素释放激素作为排卵诱导剂，在本次评估的卵泡动态与妊娠模式中未表现出显著差异。