Consentini Carlos E C, Melo Leonardo F, Lemos Motta Jessica C, Oliveira E Silva Lucas, Picoli Folchini Natália, Alves Rodrigo L O R, Madureira Guilherme, Oliveira Carneiro Tiago, Abadia Tattiany, Moroz Luis, Fortes Robson V S, Soriano Sergio, Gonzales Bruno, Wiltbank Milo C, Sartori Roberto
Department of Animal Science, University of São Paulo, Piracicaba, SP, Brazil, 13418-900; Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI 53706; GlobalGen Vet Science, Jaboticabal, SP, Brazil, 14887-360.
School of Veterinary and Animal Sciences, Federal University of Goiás, Goiânia, GO, Brazil, 74690-900.
J Dairy Sci. 2025 Jan;108(1):1138-1149. doi: 10.3168/jds.2024-25188. Epub 2024 Dec 16.
The study evaluated strategies for induction of ovulation at the end of timed AI (TAI) protocols initiated after a novel presynchronization strategy. A total of 909 lactating dairy cows from 6 dairy herds initiated a presynchronization protocol on d -15 with an intravaginal progesterone (P4) implant and 7 d later (d -8) were treated with 1.0 mg of estradiol cypionate (EC) and 0.530 mg of cloprostenol sodium (a synthetic analog of prostaglandin F; PGF), simultaneously with the P4 implant removal. On d 0, the protocol for synchronization of ovulation was initiated with 16.8 µg of buserelin acetate (a synthetic analog of GnRH) and insertion of a 2.0 g P4 implant, followed by a treatment with 0.530 mg of PGF on d 6, and a second PGF on d 7, concomitant with the P4 implant withdrawal. In Group EC, cows received 1.0 mg of EC on d 7 as an ovulation inducer. In G group, cows received 8.4 µg of GnRH 56 h after the first PGF (16 h before TAI). In Group EC/G, cows received both EC and GnRH. The TAI was performed on d 9 (48 h after P4 withdrawal) in all experimental treatments. There were no differences among treatments on pregnancy per AI (P/AI) on d 31 (40.4%; 367/909). There was a tendency for greater pregnancy loss in G group (19.8%) than in EC (12.2%) and EC/G (10.1%) groups. When the 2 groups that received EC were combined, the pregnancy loss was lower than when cows received only GnRH (11.2% [21/188] vs. 19.8% [17/86]; P = 0.05). There was an interaction between treatment and expression of estrus on P/AI, in which estrus positively affected P/AI in EC (53.3% vs. 20.0%) and EC/G (53.1% vs. 36.7%), but not in G group (41.5% vs. 38.7%). Overall, 81% of the cows had a corpus luteum (CL) on d 0 and 91% at PGF treatment of the breeding protocols. Fertility was greater in cows with CL at the time of the first PGF treatment than in cows without CL (45.9% vs. 17.7%). In summary, the strategies to induce final ovulation resulted in similar fertility despite the different physiological responses, such as expression of estrus, but further research is needed to definitively confirm the relationship between lack of EC and increased pregnancy loss.
本研究评估了在采用一种新型预同步化策略后启动的定时人工授精（TAI）方案末期诱导排卵的策略。来自6个奶牛场的909头泌乳奶牛在第 -15天开始采用阴道内孕酮（P4）植入物进行预同步化方案，7天后（第 -8天），在取出P4植入物的同时，用1.0毫克环丙孕酮（EC）和0.530毫克氯前列醇钠（前列腺素F的合成类似物；PGF）进行处理。在第0天，用16.8微克醋酸布舍瑞林（促性腺激素释放激素的合成类似物）启动排卵同步化方案，并插入一个2.0克的P4植入物，随后在第6天用0.530毫克PGF进行处理，并在第7天进行第二次PGF处理，同时取出P4植入物。在EC组，奶牛在第-7天接受1.0毫克EC作为排卵诱导剂。在G组，奶牛在第一次PGF后56小时（TAI前16小时）接受8.4微克促性腺激素释放激素。在EC/G组，奶牛同时接受EC和促性腺激素释放激素。在所有实验处理中，TAI均在第9天（P4取出后48小时）进行。在第31天，各处理间的每人工授精妊娠率（P/AI）无差异（40.4%；367/909）。G组（19.8%）的妊娠损失有高于EC组（12.2%）和EC/G组（10.1%）的趋势。当将接受EC的两组合并时，妊娠损失低于仅接受促性腺激素释放激素的奶牛（11.2%[21/188]对19.8%[17/86]；P = 0.05）。处理与发情表现对P/AI存在交互作用，其中发情对EC组（53.3%对20.0%）和EC/G组（53.1%对36.7%）的P/AI有积极影响，但对G组无影响（41.5%对38.7%）。总体而言，81% 的奶牛在第0天有黄体（CL），在繁殖方案的PGF处理时为91%。第一次PGF处理时具有CL的奶牛的繁殖力高于无CL的奶牛（45.9%对17.7%）。总之，尽管存在不同的生理反应，如发情表现，但诱导最终排卵的策略导致了相似的繁殖力，但需要进一步研究以明确证实缺乏EC与妊娠损失增加之间的关系。
