Document Type

Report

Report Number

2006-9

Publication Date

2006

Keywords

pregnancy rates, estrus, beef cow, heifers, gnrh injection, insemination

Summary

An injection of GnRH at the initiation of standing estrus has been reported to increase pregnancy and circulating concentrations of progesterone in repeat breeder dairy cows, cows that have normal estrous cycles but will not conceive. The objective of this study was to determine the effect of administering an injection of GnRH at time of insemination on subsequent concentrations of progesterone and conception rates in beef cattle that have exhibited standing estrus. Eighty-two beef heifers at 2 locations were synchronized with the Select Synch-CIDR protocol (n = 42) or the 14-19 MGA protocol (n = 40) and AI was performed following detection in standing estrus by qualified personnel. At location 1, blood samples were collected on d 2, 4, 6, 10, 15, and 18 after insemination. Heifers that were pregnant had elevated concentrations of progesterone on day 18 compared to nonpregnant heifers. Among heifers, conception rates were 71% and 59% for GnRH treated and control, respectively, and were not different between treatments. Two hundred and thirty-six postpartum beef cows at 2 locations were synchronized with the Select Synch-CIDR protocol, and AI was performed following detection in standing estrus by qualified personnel. Among cows conception rates were 70% and 70% for GnRH treated and control, respectively and were not different between treatments. Overall conception rates were 70% and 67% for GnRH treated and control, respectively, and were not different between treatments. In summary, injection of GnRH at time of insemination did not influence subsequent concentrations of progesterone and had no influence on conception rates in beef cattle that had exhibited standing estrus.

Number of Pages

4

Format

application/pdf

Language

en

Publisher

South Dakota State University

Rights

Copyright © 2006 South Dakota State University

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