Replacing the first gonadotropin-releasing hormone treatment in an Ovsynch protocol with human chorionic gonadotropin decreased pregnancies per artificial insemination in lactating dairy cows.

Autor: Cabrera EM; Department of Animal and Dairy Sciences, University of Wisconsin, Madison 53706., Lauber MR; Department of Animal and Dairy Sciences, University of Wisconsin, Madison 53706., Valdes-Arciniega T; School of Veterinary Medicine, University of Wisconsin, Madison 53706., El Azzi MS; School of Veterinary Medicine, University of Wisconsin, Madison 53706., Martins JPN; School of Veterinary Medicine, University of Wisconsin, Madison 53706., Bilby TR; Merck Animal Health, Kenilworth, NJ 07033., Fricke PM; Department of Animal and Dairy Sciences, University of Wisconsin, Madison 53706. Electronic address: pmfricke@wisc.edu.
Jazyk: angličtina
Zdroj: Journal of dairy science [J Dairy Sci] 2021 Jul; Vol. 104 (7), pp. 8290-8300. Date of Electronic Publication: 2021 Apr 08.
DOI: 10.3168/jds.2021-20274
Abstrakt: Our objective was to compare the effect of treatment with GnRH at the first treatment (G1) of the Breeding-Ovsynch portion of a Double-Ovsynch (DO) protocol with human chorionic gonadotropin (hCG) on pregnancies per artificial insemination (P/AI) in lactating dairy cows. In experiment 1, lactating dairy cows (n = 1,932) submitted to a DO protocol for first timed artificial insemination (TAI) on 2 commercial dairy farms were blocked by parity (primiparous vs. multiparous) and were randomly assigned to receive 100 µg of GnRH versus 2,500 IU of hCG at G1. Overall, P/AI 39 d after TAI for cows inseminated with sexed dairy semen was greater for cows treated with GnRH than for cows treated with hCG within each parity (primiparous: 42.6% vs. 38.2%; multiparous: 39.4% vs. 30.3%). Similarly, P/AI 39 d after TAI for multiparous cows inseminated with conventional beef semen tended to be greater for cows treated with GnRH than for cows treated with hCG (41.1% vs. 34.3%). In experiment 2, lactating Holstein cows (n = 43) were blocked by parity and were randomly assigned to the treatment protocols described for experiment 1. Ovaries were evaluated with transrectal ultrasonography immediately before treatment and 24, 28, 32, 36, and 40 h after treatment to assess time from treatment to ovulation, and blood samples were collected immediately before G1, at the first PGF 2α treatment, 8 and 16 h later, at the second PGF 2α treatment, 8 and 16 h later, at the second GnRH (G2) treatment, and at TAI to compare luteolysis based on serum progesterone (P4) concentrations. Although mean (± standard error of the mean) time from treatment to ovulation was approximately 2 h greater for cows treated with hCG than for cows treated with GnRH (33.7 ± 0.6 vs. 31.5 ± 0.6 h), P4 concentrations during luteolysis and the proportion of cows with complete luteolysis (P4 <0.4 ng/mL at G2) did not differ between treatments. We conclude that replacing 100 µg of GnRH with 2,500 IU of hCG at G1 of a DO protocol decreased fertility to TAI in lactating dairy cows but did not affect the rate or completeness of luteolysis despite the increased interval from treatment to ovulation.
(Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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