Although it induces synchronized ovulation, hCG reduces the fertility of Santa Ines ewes submitted to TAI

ABSTRACT The aim of this study was to evaluate hCG treatment on ovarian response and on pregnancy rate using a 9-day oestrus synchronization protocol in Santa Ines ewes. On a random oestrus cycle day, ewes received an intravaginal progesterone device (Primer-PR®, Tecnopec, Brazil). Nine days later (Day 9), 30µg of d-cloprostenol (Prolise®, Syntex, Argentina) and 250IU of eCG (Folligon®, Intervet, Brazil) were administered and the progesterone device was removed. This moment, the ewes were randomly assigned on two groups: Control Group and hCG Group. In the hCG Group, the ewes received 500IU of hCG (Vetecor®, Hertape-Calier, Spain) 24h after device removal. In the Control Group, the ewes did not receive any ovulation inductor. Control and hCG Groups ewes were inseminated 60h and 48h after device removal, respectively. There was no difference between the groups regarding the first ovulatory follicle diameter and the second ovulatory follicle. hCG Group ewes had shorter interval between device removal and ovulation (Control: 79.9±15.4h and hCG: 54.7±4.9h; P=0.001) and more synchronized ovulations. However, the treatment with hCG decreased the pregnancy rate after TAI (P=0,009). In conclusion, hCG administration improves ovulatory synchronisation, but causes a decrease in the pregnancy rate.

摘要
本研究旨在探究在圣塔伊内斯绵羊中采用9天发情同步方案时，人绒毛膜促性腺激素（human chorionic gonadotropin, hCG）处理对其卵巢反应及妊娠率的影响。在随机选取的发情周期当日，给母羊植入阴道孕酮装置（Primer-PR®，巴西Tecnopec公司生产）。9天后（第9天），注射30μg d-氯前列醇（d-cloprostenol，商品名Prolise®，阿根廷Syntex公司生产）与250IU孕马血清促性腺激素（equine chorionic gonadotropin, eCG，商品名Folligon®，巴西Intervet公司生产），并取出阴道孕酮装置。此时将母羊随机分为两组：对照组与hCG处理组。hCG处理组母羊在装置取出后24小时，注射500IU hCG（商品名Vetecor®，西班牙Hertape-Calier公司生产）；对照组母羊不接受任何排卵诱导剂。对照组与hCG处理组母羊分别于装置取出后60小时与48小时进行定时人工授精（timed artificial insemination, TAI）。两组母羊的首次排卵卵泡直径与第二次排卵卵泡直径均无显著差异。hCG处理组母羊的装置取出至排卵的间隔时间更短（对照组：79.9±15.4小时，hCG组：54.7±4.9小时；P=0.001），且排卵同步性更高。然而，经hCG处理会降低定时人工授精后的妊娠率（P=0.009）。综上，注射hCG可提升排卵同步性，但会降低妊娠率。