Fertility after timed breeding using GnRH, PGF2, and norgestomet

Authors

K. E. Thompson
G.C. Lamb
T.J. Marple
L.R. Corah
R.M. McKee
Jeffrey S. Stevenson
David M. Grieger
David A. Nichols

Keywords

Cattlemen's Day, 1997; Kansas Agricultural Experiment Station contribution; no. 97-309-S; Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service); 783; Beef; GnRH; PGF2; Norgestomet; Timed breeding; Anestrous suckled cows; Induced ovulation

Abstract

At the KSU Purebred Unit, 164 purebred Angus, Hereford, and Simmental cows were used to test a new estrus-synchronization program using GnRH, PGF2, and norgestomet. Cows were inseminated after detected estrus, or in the absence of estrus, inseminations were made at one fixed time after a second injection of GnRH. The treatment consisted of a 100 µg injection of GnRH plus a 6-mg ear implant of norgestomet. Seven days later, the ear implant was removed, and 25-mg of PG F2% was injected. In the absence of estrus, the time-bred group received a second injection of GnRH 48 h after PGF2% and was inseminated 16 h later. The treatment induced 10 of 36 anestrous cows to ovulate. Conception rates tended (P<.09) to be greater in Angus (72.2%) than Hereford cows (52.8%) , with conception rates in Simmental cows (51.5%) being similar to those in Hereford. Overall, pregnancy rates were similar between the time-bred group (59.3%) and the estrus-bred group (53.8%). We conclude that using GnRH, PG F2%, and norgestomet in a timed breeding program ca n eliminate the necessity of heat detection. In addition, the treatment induced estrus in 28% of the noncycling cows.

Recommended Citation

Thompson, K. E.; Lamb, G.C.; Marple, T.J.; Corah, L.R.; McKee, R.M.; Stevenson, Jeffrey S.; Grieger, David M.; and Nichols, David A. (1997) "Fertility after timed breeding using GnRH, PGF2, and norgestomet," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 1. https://doi.org/10.4148/2378-5977.1952