The Effects of Chronological Age, Weaning Weight, and Age of Dam on Angus Stayability and Lifetime Earnings

The primary objective of this study was to examine whether chronological age or weaning weight status is a more important measure of a cow’s lifetime productivity and profitability (LIFETIMEEARN). A secondary interest was investigating the stayability performance of heifers out of first calf heifers compared to heifers out of mature cows (HFC). Calving and weaning records of registered Angus cows (n = 224) from the Angelo State University ranch were compiled and sorted by varying effects (weaning weight, calving order, calving block, and age of dam). Only weaning weight (WWTBLOCK) was statistically significant (P = 0.02) for LIFETIMEEARN, with heavier calves at weaning earning more. Stayability in this study was defined as a female reaching four years of age and weaning three or more calves (3CALV). Terms that affect stayability were WWTBLOCK (P = 0.025) and CALVBLOCK (P = 0.038). The HFC variable had no effect on stayability (P = 0.42). In selecting replacement heifers these data showed it to be preferential to choose those heaviest at weaning and born early in the calving season; without regard to the age of the dam.