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Effect of gonadotropin-releasing hormone (GnRH) seven days before pre-synchronization with simultaneous prostaglandin F2α and GnRH on reproductive outcomes in Holstein dairy cows.

A. Hubner

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06-23-2020

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Abstract:

T97
Effect of gonadotropin-releasing hormone (GnRH) seven days before pre-synchronization with simultaneous prostaglandin F and GnRH on reproductive outcomes in Holstein dairy cows.
A. Hubner*1,2, P. Peixoto2, J. Hillesheim3, I. Canisso1,2, F. Lima4. 1Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois Urbana, IL, 2Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois Urbana, IL, 3Lena Veterinary Clinic Lena, IL, 4Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, CA.

The objective of this study was to improve a first-service synchronization program that was designed for farms that wish to reduce the number of treatment days of typical GnRH pre-synchronization programs. Our hypothesis was that adding a GnRH 7 d before simultaneous treatments of GnRH and PGF in a program where OvSynch started 7 d after those simultaneous treatments of GnRH and PGF would increase the percentage of cows having a CL at the start of the breeding OvSynch and thereby increase pregnancies per AI. Lactating dairy cows (n = 406) were blocked by parity and randomly assigned to control or treatment. Control cows (n = 205) received a concurrent PGF and GnRH 7 d before the first GnRH of OvSynch (GnRH-7d-PGF2α-56 h-GnRH-16h-AI). Treated cows (n = 201) received GnRH followed by concurrent PGF and GnRH in 7 d followed by the start of OvSynch in 7 d. Pregnancies/AI were similar in controls vs. treated cows on Day 32 (33% � 3.4% vs. 35% � 3.4%, P = 0.75) and Day 67 (32% � 3.3% vs. 32% � 3.4%, P = 0.88), respectively. There was tendency for an interaction between treatment and parity, with multiparous cows tending to have more pregnancies/AI to the program with the additional GnRH (P = 0.09). Percentage of cows ovulating to the GnRH of the simultaneous treatments of GnRH and PGF was not different between control and treatment, nor was there a difference in the percentage of cows starting the breeding OvSynch with a CL. In summary, addition of a GnRH treatment 7 d before simultaneous treatments of GnRH and PGF2α administered 7 d before the start of OvSynch did not improve ovulatory response to the GnRH of the simultaneous GnRH and PGF, nor did it increase pregnancies per AI.

Keywords: presynchronization, timed AI, anovular.