108 Pregnancy rates to embryo transfer in lactating Bos indicus × Bos taurus dairy cows synchronized with a new gonadotropin-releasing-hormone based protocol with lengthened proestrus
A. V. Cedeño A B , F. Paucar A , L. Pinargote A , B. Mendoza A , V. Ocampo A , G. Romero A and G. A. Bó B CA
B
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This experiment evaluated recipients utilisation rate and pregnancy outcomes to embryo transfer (P/ET) in lactating Bos indicus × Bos taurus cows (Gyr × Jersey) synchronized with an oestradiol-based protocol or with a new GnRH-based protocol with a lengthened proestrus (named “Web-Synch”). Lactating cows (n = 1456) with 55.0 ± 12.0 days in milk, a corpus luteum (CL) or at least one follicle >8 mm in diameter (determined by ultrasonography), a body condition score between 2.5 and 4 (1–5 scale) and managed in a confinement system, were randomly allocated into one of two treatment groups. On Day 0, cows in the J-Synch group (n = 711) received 2 mg of oestradiol benzoate (EB, Calier) and an intravaginal device containing 1.2 g of progesterone (P4, Pluselar, Calier). On Day 6, P4 devices were removed, and all cows received 150 µg D (+) cloprostenol (PGF, Veteglan, Calier), 400 IU of equine chorionic gonadotropin (eCG; Vetegon, Calier). Cows in the Web-Synch group (n = 675) were treated with prostaglandin F2α (PGF) and P4 device on Day −5, 10 µg of buserelin (GnRH, Pluserelina, Calier) on Day 0 and P4 device removal, PGF and eCG on Day 6. All cows were observed for signs oestrus, which was based on tail-paint removal (>50%), by 72 h after P4 device removal. In those detected in oestrus their ovaries were examined by ultrasonography (Mindray M6 Vet) on Day 16 and those with a CL >16 mm in diameter received a grade 1 in vitro-produced blastocysts by nonsurgical transfer. Recipients without their tail-paint removed were not transferred. Pregnancy was determined by ultrasonography 30 and 90 days after embryo transfer. Data were analysed using the GLM mixed procedure for binary data with a logit link (InfoStat, 2022) and results are presented in Table 1. Although the utilisation rate did not differ among groups, the Web-Synch protocol resulted in greater P/ET that the J-Synch protocol.
Treatment groups | Utilisation rate | P/ET 30 days | P/ET 90 days | Pregnancy losses 30–90 days | |
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Web-Synch | 95.0% (641/675) | 43.1%b (276/641) | 40.4%b (256/641) | 7.8% (20/276) | |
J-Synch | 91.0% (711/781) | 30.0%a (213/711) | 28.1%a (200/711) | 6.1% (13/213) |
a,bWithin a column, values with different superscripts differ (P < 0.05).