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Evaluation of GnRH- versus estradiol-based protocols for ovulation synchronization in postpartum Bos taurus grazing beef cows submitted to fixed-time artificial insemination

This study compared the effect of a 7-day estradiol- and a 7-day GnRH-based FTAI protocol versus a presynchronized GnRH-based FTAI protocol (7 & 7 GnRH) on pregnancy per AI (P/AI) in multiparous postpartum Angus cows. Cows were blocked according to presence/absence of a CL, body condition score, and...

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Main Authors: Ferre, Luis Bernardo, Cerviño, Maria Natalia, Jaeschke, Julian, Itterman, Maximiliano, McLean, Jaime, Aragon, Agustin, Fernández, Manuel, Villa, Matías, Formia, Néstor, Jaureguiberry, Maria, Rearte, Ramiro, Kjelland, Michael E., Colazo, Marcos G., Thomas, Jordan M., De la Sota, Rodolfo Luzbel
Format: info:ar-repo/semantics/artículo
Language:Inglés
Published: Elsevier 2025
Subjects:
Bos taurus
Beef Cattle
Oestrus Synchronization
Perinatal Period
Estradiol
GnRH
Artificial Insemination
Ganado de Carne
Sincronización del Celo
Período Perinatal
Inseminación Artificial
Online Access:http://hdl.handle.net/20.500.12123/20800
https://www.sciencedirect.com/science/article/abs/pii/S0093691X24004618
https://doi.org/10.1016/j.theriogenology.2024.11.008
Summary:This study compared the effect of a 7-day estradiol- and a 7-day GnRH-based FTAI protocol versus a presynchronized GnRH-based FTAI protocol (7 & 7 GnRH) on pregnancy per AI (P/AI) in multiparous postpartum Angus cows. Cows were blocked according to presence/absence of a CL, body condition score, and days postpartum and assigned randomly to one of three treatments: I) 7-day EB (n = 368), estradiol benzoate (EB) and intravaginal progesterone-(P4)-releasing device (IVPD) on Day −10, prostaglandin F2α (PG), equine chorionic gonadotropin (eCG) and estradiol cypionate (ECP) at IVPD removal on Day −3 with FTAI done on Day −1 (54 ± 2 h after IVPD removal); II) 7-day GnRH (n = 367), GnRH at IVPD insertion on Day −10, PG and eCG at IVPD removal on Day −3 with GnRH and FTAI on Day 0 (66 ± 2 h after IVPD removal); and III) 7 & 7 GnRH (n = 361), PG at IVPD insertion on Day −17, GnRH on Day −10, IVPD removal, PG and eCG on Day −3 with GnRH and FTAI on Day 0 (66 ± 2 h after IVPD removal). Preovulatory follicle diameter, corpus luteum (CL) presence, CL area, and P4 concentration were determined at IVPD removal, as well as estrus expression at FTAI and P/AI between 35 and 40 days after FTAI. Plasma P4 concentrations at IVPD removal were greater (P < 0.05) in cows subjected to the 7-day GnRH or 7 & 7 GnRH protocols and a greater number of cows (P < 0.05) had at least one CL at IVPD removal compared to cows subjected to the 7-day EB protocol. However, the 7 & 7 GnRH protocol resulted in more cows with two CLs at IVPD removal compared to the other two protocols. Moreover, cows synchronized with the 7 & 7 GnRH protocol had larger preovulatory follicles (P < 0.05) and larger CL area at IVPD removal (P < 0.05), and a greater rate of estrus expression before FTAI (P < 0.05) than cows synchronized with the 7-day EB, whereas those variables were intermediate in cows synchronized with the 7-day GnRH. Pregnancy per AI was greater (P < 0.05) in cows treated with the 7 & 7 GnRH (63.5 %) treatment compared to the 7-day EB (51.4 %) and the 7-day GnRH (51.3 %) protocols. In summary, the 7 & 7 GnRH protocol enhanced circulating P4 before IVPD removal, increased estrus expression rate before FTAI, and improved P/AI in postpartum Bos taurus grazing beef cows.

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