Effect of an additional gonadotropin-releasing hormone 2 days after the initiation of a resynchronization program 25 days after artificial insemination on fertility of lactating dairy cows

• Published in: JDS communications 2024-11, Vol.5 (6), p.695-699
• Main Authors: Leão, Iago Matheus Rosa, Carbajal, Anthony, Narciso, César, Consentini, Carlos Eduardo Cardoso, Sartori, Roberto, Nascimento Martins, João Paulo
• Format: Article
• Language: English
• Subjects: Physiology
• ISSN: 2666-9102; 2666-9102
• DOI: 10.3168/jdsc.2023-0540

[Display omitted] •G25&27 did not decrease nonpregnant cows without CL at day 32.•G25&27 did not improve the overall fertility of primiparous cows.•G25&27 was associated with a reduced P/AI of the previous AI in multiparous cows.•G25&27 decreased pregnancy loss of AI after treatment in multiparous cows.•G25&27 tended to increase calving per AI for AI after treatment in multiparous cows. We investigated the effect of an additional GnRH 2 d after initiation of resynchronization on d 25 post-AI on the proportion of cows without a corpus luteum (CL) at nonpregnancy diagnosis (NPD) and pregnancy per AI (P/AI) of cows with a CL at NPD that were reinseminated. Once per week, cows that were inseminated 25 d earlier were randomly assigned to receive either a GnRH treatment only (G25) or GnRH on this day and 2 d later (G25&27). Pregnancy diagnosis and CL presence were determined d 32 post-AI using ultrasonography. Nonpregnant cows with a CL were enrolled in different strategies for resynchronization of ovulation according to parity (primiparous or multiparous) and CL size. Primiparous and multiparous cows with a CL ≥20 mm in diameter continued Resynch-25 (PGF2α on d 32; PGF2α on d 33; GnRH on d 34; and AI on d 35). Multiparous cows with CL