Ferré Luis B, Jaeschke Julian, Gatti Juliana, Baladón Gerardo, Bellocq Ezequiel, Fernández Gustavo, Rearte Ramiro, Kjelland Michael E, Colazo Marcos G, Thomas Jordan M
National Institute of Agricultural Technology (INTA), Chacra Experimental Integrada Barrow (MDA-INTA), Tres Arroyos B7500, Buenos Aires, Argentina.
Departamento Técnico de Biogénesis Bagó S.A., Garin B1619, Buenos Aires, Argentina.
Animals (Basel). 2023 Sep 4;13(17):2803. doi: 10.3390/ani13172803.
Fixed-timed artificial insemination (FTAI) protocols for beef cattle in South America are primarily based on estradiol esters and intravaginal progesterone-releasing devices (IVPD). The objective of this study was to determine the optimal gonadotropin-releasing hormone (GnRH)-based protocol as an alternative to the use of estrogen-based protocols in grazing suckling beef cows. All cows received an IVPD on the day of protocol initiation and prostaglandin F (PG) plus equine chorionic gonadotropin (eCG) treatments at the time of IVPD removal. In Experiment 1, cows (n = 235) were randomly assigned to one of four treatments: (i) 7-day estradiol = 2 mg of estradiol benzoate (EB) at IVPD insertion on Day 9 and 1 mg of estradiol cypionate (ECP) at IVPD removal on Day 2; (ii) 7-day GnRH = 10 µg of GnRH at IVPD insertion on Day 10, IVPD removal on Day 3 and GnRH at FTAI; (iii) 7 & 7 estradiol = PG at IVPD insertion on Day 16, EB on Day 9 and ECP at IVPD removal on Day 2; (iv) 7 & 7 GnRH = PG at IVPD insertion on Day 17, GnRH on Day 10, IVPD removal on Day 3 and GnRH at FTAI. In Experiment 2, cows (n = 462) were randomly assigned to one of four treatments: (i) 6-day estradiol = EB at IVPD insertion on Day 9, IVPD removal on Day 3 and GnRH at FTAI; (ii) 7-day estradiol; (iii) 7-day GnRH; (iv) 7 & 7 GnRH. In Experiment 1, plasma progesterone concentrations and percentage of cows with a corpus luteum (CL) at IVPD removal, and pregnancy per AI (P/AI) were greater for cows subjected to GnRH-based protocols compared with cows subjected to estrogen-based protocols ( < 0.01). In Experiment 2, cows subjected to the 7 & 7 GnRH protocol had the greatest P/AI ( < 0.01). In summary, GnRH-based FTAI protocols resulted in similar or greater P/AI compared to estrogen-based FTAI protocols in grazing postpartum suckled beef cows. The greatest P/AI was attained with the 7 & 7 GnRH protocol.
南美洲肉牛的定时人工授精（FTAI）方案主要基于雌二醇酯和阴道内孕酮释放装置（IVPD）。本研究的目的是确定基于促性腺激素释放激素（GnRH）的最佳方案，以替代在放牧哺乳肉牛中使用基于雌激素的方案。所有母牛在方案开始当天接受IVPD，并在IVPD取出时接受前列腺素F（PG）加马绒毛膜促性腺激素（eCG）处理。在实验1中，母牛（n = 235）被随机分配到四种处理之一：（i）7天雌二醇 = 在第9天插入IVPD时注射2毫克苯甲酸雌二醇（EB），在第2天取出IVPD时注射1毫克环丙孕酮（ECP）；（ii）7天GnRH = 在第10天插入IVPD时注射10微克GnRH，在第3天取出IVPD，并在FTAI时注射GnRH；（iii）7 & 7雌二醇 = 在第16天插入IVPD时注射PG，在第9天注射EB，在第2天取出IVPD时注射ECP；（iv）7 & 7 GnRH = 在第17天插入IVPD时注射PG，在第10天注射GnRH，在第3天取出IVPD，并在FTAI时注射GnRH。在实验2中，母牛（n = 462）被随机分配到四种处理之一：（i）6天雌二醇 = 在第9天插入IVPD时注射EB，在第3天取出IVPD，并在FTAI时注射GnRH；（ii）7天雌二醇；（iii）7天GnRH；（iv）7 & 7 GnRH。在实验1中，与接受基于雌激素方案的母牛相比（P < 0.01），接受基于GnRH方案的母牛在IVPD取出时血浆孕酮浓度、有黄体（CL）的母牛百分比以及每次人工授精后的妊娠率（P/AI）更高。在实验2中，接受7 & 7 GnRH方案的母牛P/AI最高（P < 0.01）。总之，在放牧的产后哺乳肉牛中，与基于雌激素的FTAI方案相比，基于GnRH的FTAI方案导致相似或更高的P/AI。7 & 7 GnRH方案获得了最高的P/AI。
