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Barbosa IP, Cestaro JP, Silva SA, et al. GnRH34: An alternative for increasing pregnancy in timed AI beef cows. Theriogenology. 2021;179:1-6doi: 10.1016/j.theriogenology.2021.11.014.
Barbosa, I. P., Cestaro, J. P., Silva, S. A., Noleto, G. S., Gonçalves, R. L., Silva, G. M., Paes, F. H., Gasperin, B. G., Rovani, M. T., & Pfeifer, L. F. M. (2021). GnRH34: An alternative for increasing pregnancy in timed AI beef cows. Theriogenology, 1791-6. https://doi.org/10.1016/j.theriogenology.2021.11.014
Barbosa, Ingrid P, et al. "GnRH34: An alternative for increasing pregnancy in timed AI beef cows." Theriogenology vol. 179 (2021): 1-6. doi: https://doi.org/10.1016/j.theriogenology.2021.11.014
Barbosa IP, Cestaro JP, Silva SA, Noleto GS, Gonçalves RL, Silva GM, Paes FH, Gasperin BG, Rovani MT, Pfeifer LFM. GnRH34: An alternative for increasing pregnancy in timed AI beef cows. Theriogenology. 2021 Nov 17;179:1-6. doi: 10.1016/j.theriogenology.2021.11.014. Epub 2021 Nov 17. PMID: 34823056.
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Theriogenology. 2021 Nov 17;179:1-6. doi: 10.1016/j.theriogenology.2021.11.014. Epub 2021 Nov 17.

GnRH34: An alternative for increasing pregnancy in timed AI beef cows.

Theriogenology

Ingrid P Barbosa, Jamyle P Cestaro, Samira A Silva, Gabrielly S Noleto, Reuel L Gonçalves, George M Silva, Felipe H Paes, Bernardo G Gasperin, Monique T Rovani, Luiz F M Pfeifer

Affiliations

  1. Universidade Federal do Acre, UFAC, PPGESPA, Rio Branco, Acre, Brazil.
  2. Centro Universitário Aparício Carvalho - FIMCA, Porto Velho, RO, Brazil.
  3. Biogénesis Bagó Saúde Animal, Curitiba, PR, Brazil.
  4. Universidade Federal de Rondonia - UNIR, PPG em Desenvolvimento Regional e Meio Ambiente, Porto Velho, RO, Brazil.
  5. Universidade Federal de Pelotas - UFPEL, PPG em Veterinária, Pelotas, RS, Brazil.
  6. Universidade Federal do Rio Grande do Sul - UFRGS, PPG em Ciências Veterinárias, Porto Alegre, RS, Brazil.
  7. Embrapa Rondonia, Brazilian Agricultural Research Corporation, Porto Velho, RO, Brazil. Electronic address: [email protected].

PMID: 34823056 DOI: 10.1016/j.theriogenology.2021.11.014

Abstract

Two experiments evaluated the effects of gonadotropin releasing hormone (GnRH) treatment on fertility of suckled Nelore beef cows treated with an estradiol/progesterone (P4)-based protocol for timed artificial insemination (TAI). Experiment 1 was designed to determine the effect of GnRH administered 34 h after P4 insert removal (GnRH34) on time of ovulation. Suckled cows (n = 34) were treated with 2 mg estradiol benzoate (EB) and an intravaginal insert containing 1.9 g of P4. Eight days later, P4 inserts were removed, and all cows received 150 μg of d-cloprostenol (prostaglandin F2 alpha analogue), 300 IU of eCG, and 1 mg of estradiol cypionate (ECP). On Day 9 (05:00 p.m.), cows were randomly distributed, according to the diameter of the pre-ovulatory follicle, in two treatments: 1) GnRH (n = 17) cows that received 10.5 μg of buserelin acetate, or 2) no further treatment (control, n = 17). Cows treated with GnRH 34 h after P4 insert removal ovulated earlier (P = 0.02) than control cows (66 ± 0.0 and 77.2 ± 4.3 h). Experiment 2 was designed to determine the effect of GnRH34 on the fertility of suckled beef cows. Nelore cows (n = 506) were treated as Experiment 1. On Day 8, cows were painted in the sacrocaudal region to identify cows that displayed estrus. On Day 9 (05:00 p.m.), cows were randomized to receive same treatment as Experiment 1, control (n = 252), or GnRH (n = 254). All cows were TAI 48 h after P4 insert removal. At TAI, estrus was evaluated, and deemed to have occurred in cows without a tail-head chalk mark (>75% paint loss). Cows treated with GnRH 34 h after P4 insert removal had greater (P = 0.01) pregnancy per AI (P/AI) than cows that only received ECP (63.0% and 50.4%). No difference (P = 0.5) was observed in the proportion of cows that displayed estrus between treatments. Furthermore, cows that displayed estrus had greater (P < 0.01) P/AI than cows that did not. Treatment with GnRH, given at 34 h after P4 insert removal, increased (P < 0.05) P/AI in cows that did not show estrus at TAI. In summary, treatment with GnRH 34 h after P4 insert removal was associated with earlier ovulation and resulted in greater P/AI in suckled Nelore cows treated with an estradiol/P4-based protocol for TAI.

Copyright © 2021. Published by Elsevier Inc.

Keywords: Beef cattle; Fertility; Ovulation; Pregnancy

Conflict of interest statement

Declaration of competing interest The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartially of the research reported.

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