Differences in lifetime productivity of beef heifers that conceived to first-service artificial insemination (AI) or a clean-up bull via natural service (NS) as a yearling and among females that were offspring of an AI or NS mating

The objectives of this study were to compare lifetime productivity between heifers that conceived to AI or a clean-up bull via natural service (NS) as yearlings, and among females that were offspring of an AI or NS mating. Records (n = 6,693) on 1,173 females subjected to estrus synchronization and AI, with NS beginning approximately 10 d later, at one location from 1991 to 2010 were used. For the first objective, females were classified as conceiving to AI or NS as yearlings based on a 290-d gestation length added to the AI date. For the second objective, females were grouped into 1 of 4 dam classifications if they were the offspring of a 1) primiparous heifer that conceived to AI, 2) primiparous heifer that conceived to NS, 3) multiparous cow that conceived to AI, or 4) multiparous cow that conceived to NS. Lifetime revenue was calculated using price and weaning weight data for each calf produced. Actual and average market prices, as well as synthetic price regimens representing extreme weight-price interactions, were used. As yearlings, females that conceived to AI had greater (P < 0.0001) lifetime weight weaned, calves weaned, and revenue under all price scenarios and greater (P < 0.05) calf weaning weight than did females that conceived to NS. Dam classifications did not differ (P > 0.10) for any variables. In conclusion, when estrus synchronization and AI are used before NS, yearling heifers conceiving earlier to AI can achieve greater lifetime productivity than can heifers conceiving later to NS.