Effects of Weaning Productivity, as Mediated Through Sire Selection, on Subsequent Pregnancy Rate of the Cow Herd1,2

The present study, conducted to determine the impact of level of weaning productivity on subsequent pregnancy rate of the cow herd, involved two locations in the Southern Region - University of Kentucky, Lexington and Hill Farm Research Station, Louisiana State University Agricultural Center, Homer. Differences in level of (WW) productivity were created by producing calves sired by high and average bulls selected on the basis of direct WW expected progeny differences (EPD) (Kentucky: low-accuracy yearling Limousin bulls, natural matings, 478 calvings, direct WW EPD between high and average bulls = 11.3 kg; Louisiana: high-accuracy Simmental bulls, AI matings, 120 calvings, direct WW EPD between high and average bulls = 9.2 kg). Realized differences for 205-d WW between high- and average-sired progeny were 13 kg (P<0.05) and 16 kg (P<0.01), respectively, for the Kentucky and Louisiana locations; however, these realized differences did not have a significant impact on subsequent pregnancy rate of the cow herd at either location. Cows weaning high- and average-sired calves had subsequent pregnancy rates of 93.3 and 96.6%, respectively, at the Kentucky location and 94.7 and 92.4%, respectively, at the Louisiana location.