Factors Influencing Weaning Weight in the Hereford Cattle and Adjustment Factors to Correct Records for these Effects

Abstract

Weaning weight records from 606,967 registered Hereford calves were provided for analysis by the American Hereford Association. Mixed model procedures were used to examine the relative importance of sex of calf, region of the United States, age of dam, and the two-factor interactions among these effects after adjustment for the random effects of herds within region, contemporary groups within herd and cows within herd. The combined random effects accounted for 65% of the total corrected sum of squares (TCSS) in weaning weight, and the combined fixed effects accounted for 7% of the TCSS, while 28% of the TCSS was unexplained by the model. Of the fixed effects considered, only sex of calf and age of dam appeared to be biologically significant, even though all main effects and all two-way interactions were statistically significant. Based on these results, correction factors were developed for adjusting 205-d adjusted weaning weights of Hereford cattle to a bull-calf-raised-by-a-mature-cow basis.