Protocol with nine days of progesterone for fixed-time artificial insemination in Bos taurus cows adapted to the tropical weather

ABSTRACT Three experiments were performed to adapt a synchronization protocol of estrus synchronization and ovulation to be used in fixed time artificial insemination programs (FTAI) in tropically adapted Bos taurus cows. In Exp. 1 (crossover) multiparous Curraleiro Pé-Duro cows (n= 12) received an intravaginal device containing 1g of P4 for 8 days and 2mg of EB at the time of device insertion (Day 0). On the P4 device removal (Day 8) females received 150g of D-cloprostenol Sodic and 300IU of equine chorionic gonadotropin (eCG). Then, they were randomly divided to receive 1mg of EB on Day 8 (EB8) or on Day 9 (EB9). EB9 delayed ovulation approximately 15 hours (P<0.05). In Exp. 2, protocols using progesterone for eight (P4D8) or nine days (P4D9) were evaluated, resulting in similar parameters of folicular and luteal development (P>0.05). In Exp. 3, EB8 and P4D9 protocols were used to evaluate the pregnancy rate, reaching 23% (10/43) and 20% (9/45), respectively (P>0.05). Although P4D9 protocol has shown improvement in proportion of animals that responded to the protocol when compared to EB8 protocol, it was not able to improve pregnancy rate.

摘要：本研究开展3项试验，旨在将发情同步与排卵同步方案适配于热带适应型普通牛（Bos taurus）的定时人工授精（FTAI）项目。试验1为交叉设计试验，选取12头经产库拉莱罗佩杜罗（Curraleiro Pé-Duro）牛，于试验第0天植入含1克孕酮（P4）的阴道内置装置，装置植入周期为8天，植入当日同时注射2毫克苯甲酸雌二醇（EB）；于第8天撤除孕酮阴道内置装置时，受试母牛注射150克氯前列醇钠（D-cloprostenol Sodium）与300国际单位马绒毛膜促性腺激素（eCG），随后将其随机分为两组，分别于第8天（EB8组）或第9天（EB9组）注射1毫克苯甲酸雌二醇。结果显示，EB9组可使排卵延迟约15小时（P<0.05）。试验2评估了孕酮植入时长为8天（P4D8组）与9天（P4D9组）的两种方案，二者的卵泡发育与黄体发育参数无显著统计学差异（P>0.05）。试验3采用EB8与P4D9两种方案评估妊娠率，两组妊娠率分别为23%（10/43）与20%（9/45），组间无显著统计学差异（P>0.05）。尽管与EB8方案相比，P4D9方案可提升受试动物的方案应答率，但未能改善妊娠结局。