Affiliation:
1. Faculdade de Veterinária Universidade Federal do Rio Grande do Sul Porto Alegre RS Brazil
2. Faculdade de Veterinária, FiBRA Universidade Federal de Pelotas Capão do Leão RS Brazil
3. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Porto Velho RO Brazil
Abstract
ABSTRACTThe study aimed to evaluate the effects of GnRH given 34 h after progesterone (P4) intravaginal device (IVD) removal in a timed artificial insemination (TAI) protocol. In Experiment 1, 17 Hereford and Braford heifers (control, n = 7; GnRH34; n = 10) received 2 mg estradiol benzoate (EB) and a 1 g P4 IVD on Day 0 (D0). On D8, IVDs were removed and 150 μg d‐cloprostenol (PGF) and 1 mg estradiol cypionate (EC) were administered. In the GnRH34 group, animals received 25 μg lecirelin 34 h after the IVD removal (D9). TAI was performed in both groups on D10 (48 h after IVD removal). Follicular dynamics were evaluated from D8 until ovulation; blood samples were collected 7 and 12 days after TAI. In Experiment 2, to evaluate the effect of GnRH34 on pregnancy rates (control, n = 187; GnRH34; n = 203), heifers were subjected to the TAI protocols described in Experiment 1. No significant differences were observed in preovulatory follicle (POF) diameter on D10, follicular growth and ovulation rates until 72 h and P4 concentrations on days 7 and 12 after TAI (p > 0.05). Pregnancy rates (PR) were similar between groups (Control = 50.2%; GnRH34 = 50.2%; p = 0.65). A significant effect of body weight (BW) and body condition score (BCS) on PR was observed for control (p< 0.05), but not for GnRH34. In conclusion, GnRH 34 h after the IVD removal in beef heifers previously treated with EC had no effect on luteal function and fertility.
Funder
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul
Reference24 articles.
1. GnRH34: An alternative for increasing pregnancy in timed AI beef cows
2. Baruselli P. S.2023.“Com Desaceleração de 5% em 2022 Mercado da IATF Registra Primeiro Recuo em 20 Anos 7th ed Boletim Eletrônico do Departamento de Reprodução Animal/FMVZ/USP.”
3. History, Evolution and Perspectives of Timed Artificial Insemination Programs in Brazil;Baruselli P. S.;Animal Reproduction,2012
4. Split-time artificial insemination in beef cattle: I–Using estrous response to determine the optimal time(s) at which to administer GnRH in beef heifers and postpartum cows
5. Synchronization Techniques to Increase the Utilization of Artificial Insemination in Beef and Dairy Cattle;Bó G. A.;Animal Reproduction,2018