Insulin effect during a Heatsynch protocol in dairy cows

ABSTRACT: The objective of this study was to evaluate the effect of exogenous insulin administration on follicular growth, estrus presentation and conception rate during a protocol of ovulation synchronization. Dairy cows were subjected to the Heatsynch protocol, with the insertion of an intravaginal device containing 1.9 g of progesterone (CIDR) and an intramuscular injection containing 2.5 mg of GnRH on day 0. On day 7, the CIDR was removed and subjects were given 12.5 mg of dinoprost. Also on day 7, Insulin Group (IG, n = 21) animals received a subcutaneous injection containing 0.25 IU / kg of recombinant human insulin and the control group (CG, n = 25) received a 0.9% NaCl injection. On day 8, an injection of 0.5 mg of estradiol cypionate was administered to all cows. Animals were inseminated 12 hours after estrus presentation or at day 10 at fixed time. Follicular development was evaluated on days 7, 9, and 10 using transrectal ultrasonography, estrus presentation was observed between days 8 and 10, and conception rate was evaluated 30 days after AI. There were no differences in growth rate, follicular diameter, estrus presentation, and conception rate. Therefore, application of a single dose of insulin does not promoted an increase in follicular size, estrus presentation and conception rate in dairy cows.摘要：本研究旨在评估排卵同步化方案中，外源性胰岛素给药对泌乳奶牛卵泡发育、发情表现及受胎率的影响。试验牛均采用Heatsynch同步发情方案：于第0天插入含1.9g孕酮的阴道植入装置（CIDR），并肌肉注射2.5mg促性腺激素释放激素（GnRH）。第7天移除CIDR，并为所有受试牛肌肉注射12.5mg地诺前列素；同日，胰岛素组（IG，n=21）接受皮下注射0.25 IU/kg重组人胰岛素，对照组（CG，n=25）注射0.9%氯化钠注射液。第8天，为所有奶牛注射0.5mg环丙酸雌二醇。受试牛于发情表现出现后12小时或第10天进行定时人工授精（Artificial Insemination，AI）。分别于第7、9、10天采用直肠超声检查评估卵泡发育情况，于第8至10天观察发情表现，并于人工授精后30天评估受胎率。各组在生长速率、卵泡直径、发情表现及受胎率方面均无显著差异。因此，单次注射胰岛素并不会提升泌乳奶牛的卵泡尺寸、发情表现及受胎率。