Repeatability of Weaning Traits in Beef Cattle1

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Abstract
The repeatability of average daily gain from birth to weaning (ADG) and type score at weaning (TS) has been estimated from a population of 4,838 weaning records of the Hereford and Angus breeds. The records were first adjusted for sex, age-of-dam and year differences. The assumptions involved in the use of the regression estimator of repeatability were examined, and this estimator was used to compute repeatability from all available pairs of records made by cows aged 10 years or less. The values obtained agree with most estimates in the literature. The adjacency effect which is evident indicates that early records are a poor basis for prediction of performance more than 2 years removed. An adjacent record may be predicted with reasonable accuracy for ADG (repeatability=0.48) and less well for TS (repeatability=0.28). The variance of the corrected records for ADG decreased slightly with increasing age of dam. This may indicate more genetic homogeneity at older ages due to selection on earlier records. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science