Is it possible to replace eCG by GnRH in the hormonal protocol for timed artificial insemination in ewes during the breeding season?

Autor: Maggi G; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Pires OS; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Junior SFV; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Oliveira FC; Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil., Moraes FP; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Ferreira R; Universidade do Estado de Santa Catarina, Chapecó, SC, Brazil., Vieira AD; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Rovani MT; Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil., Gonçalves PBD; Universidade Federal de Santa Maria, Santa Maria, RS, Brazil., Mondadori RG; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil., Gasperin BG; FiBRA, Faculdade de Veterinária, Universidade Federal de Pelotas, s/n - Caixa Postal 354 - Campus Universitário, Capão do Leão, RS CEP: 96160-000, Brazil. Electronic address: bggasperin@gmail.com.
Jazyk: angličtina
Zdroj: Domestic animal endocrinology [Domest Anim Endocrinol] 2024 Oct; Vol. 89, pp. 106878. Date of Electronic Publication: 2024 Aug 04.
DOI: 10.1016/j.domaniend.2024.106878
Abstrakt: Hormonal protocols based on progestogens and equine chorionic gonadotrophin (eCG) are efficient for estrus and ovulation synchronization in ewes. Although eCG is indispensable during seasonal anestrus, it may not be necessary during the breeding season. Thus, we tested the hypothesis that GnRH is effective in replacing eCG during the breeding season allowing satisfactory ovulation rate, luteal function and conception rates after timed artificial insemination (TAI). Ewes (n = 134) with a minimum body condition score of 2.5 (0-5 scale) were treated with intravaginal devices (IVD) containing 60 mg of medroxyprogesterone acetate (MPA) for seven days and received 0.26 mg of sodium cloprostenol at the time of IVD removal. In Exp. 1, at IVD removal, ewes (n = 29) were allocated to three groups: eCG (200 IU at IVD removal; n = 10); eCG+GnRH (200 IU eCG at IVD removal and 4 µg of buserelin 36 h later; n = 10); or GnRH (buserelin 36 h after IVD removal; n = 9). Blood samples were collected 2, 6 and 12 days after TAI moment (54 h after IVD removal), for progesterone (P4) analysis. In Exp 2, the ewes were allocated to eCG (n = 10) or GnRH (n = 10) groups, as above described, and ovulation moment was evaluated 54, 66 and 78 h after IVD removal. In Exp 3, TAI was performed in ewes from eCG (n = 45) and GnRH (n = 40) groups using 100 × 10 6 motile spermatozoa from a pool of semen collected from four rams. In Exp. 1, based on P4 levels, we confirmed that all the ewes ovulated (29/29) and there was no significant effect of group (P = 0.89) or group x day (P = 0.18) on P4 concentration, being observed a significant effect of day (P = 0.0001). In Exp. 2, the maximum DF diameter (P = 0.26) and ovulation moment (P = 0.69) did not differ between groups. In Exp. 3, pregnancy rate was significantly lower (P = 0.02) in GnRH (22.5 %; 9/40) compared to eCG (46.7 %; 21/45). The results indicate that, although ovulation and luteal function were not altered after eCG, eCG+GnRH or GnRH treatment, GnRH alone before TAI cannot be used to replace eCG treatment during the breeding season.
Competing Interests: Declaration of competing interest The authors declare no conflicts of interest.
(Copyright © 2024 Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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