Hormonal adjustments for fixed-time artificial insemination and physiologic variables influence in the reproductive performance of Bos indicus heifers

• Autor(a) principal: Acosta Galindez, Juan Pablo
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/11/11139/tde-14102022-104611/
• topic: Bos indicus; Bos indicus; Fertilidade; Fertility; GnRH; GnRH; Heifers; IATF; Novilhas; Prostaglandin; Prostaglandina; TAI

The present study aimed to evaluate the effect of different hormonal treatments and the understanding of some physiological variables on the ovarian dynamics and the reproductive outcomes of Bos indicus heifers submitted to a 7d estradiol (E2)/progesterone (P4)-based timed artificial insemination (TAI) protocol. Was performed using Nelore heifers with an average of 16.0 ± 0.03 months of age. Were included just heifers that were non pregnant 30 days after a first AI being resynchronized. On Day -9 all heifers received an intravaginal P4 implant for 7 days and estradiol benzoate (EB). On Day -2, had the implant removed and at the same time was administered estradiol cypionate (EC), equine chorionic gonadotropin (eCG), and prostaglandin F2α (PGF). On Day 0,48 hours after the implant withdrawn, all heifers were AI. Also, there were two factors analyzed, one of them was the administration of PGF (PGF1) or not (PGF0) at the P4 implant insertion time. The other one was the GnRH treatment at the AI time (G1) or not (G0), resulting in four different treatments (PGF0G0, PGF0G1, PGF1G0 and PGF1G1). The expression of estrus until the TAI, was evaluated with the use of Tail-chalk, the ultrasound of the ovaries was performed on Days -9, -2, 0, and the pregnancy diagnose was executed 30 and 60 days after AI. The P/AI on Day 60 had no difference between the treatments, the PGF on Day -9 had no influence on the P/AI of the heifers with CL at the beginning of the TAI protocol. Heifers with expression of estrus achieved a better P/AI as there was a lower pregnancy loss for this group. The GnRH administration did not generate difference within the group without estrus, as there was no influence of this hormonal treatment on the general P/AI. On the other hand, the P/AI tended to increase just in the youngest heifer’s group that had higher body weight, having no effect for the older heifers. Also, the lightest females with an older age had a higher probability of pregnancy, what did not occur for the heavier heifer’s groups. This study allows to conclude, that the treatments proposed did not impact on the heifers fertility. Better reproductive performance was achieved by the older heifers, and the higher body weight might improve the P/AI of youngest heifers.