Estimation of Genetic and Environmental Factors Affecting Weaning Weights of Creep-Fed Cattle

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Abstract
Data from 1,861 creep-fed calves raised during 1957, 1958, and 1959 were analyzed. Assuming that each weaning weight could be expressed as a linear combination of a sex effect, an age of dam effect, and an age of calf effect, least squares analyses were performed on an among- and within-year basis. Each source of variation was highly significant, so factors were obtained to adjust the weights of heifers to correspond to those of steers, and to adjust for age of dam to a mature equivalent. Sex of calf and age of dam constants were much larger than those previously published for noncreep-fed calves. Searle's simplified method, involving a multiplicative factor based on subclass means was also used to obtain adjustments on a within-year basis. Comparing the reduction in sums of squares by the two methods, measures of relative efficiency of 99.2, 97.9, and 99.1% were found for Searle's method for 1957, 1958, and 1959 respectively. Since ease of computation is added to the apparently high relative efficiency of Searle's method, it appears to be useful for individual herds on a within-year basis. A paternal half-sib correlation of 0.12 was obtained by pooling the 458, 405, and 471 paternal half-sib records obtained in the 3 respective years. When this was compared with a coefficient based on 771 maternal half-sib records, the difference between paternal and maternal half-sib correlations was found to be nonsignificant. The estimate of heritability based on paternal half-sib records was 0.47. The 332 full-sib records obtained during 1958 and 1959 yielded an intraclass correlation of 0.37; after the maternal effect was deleted, a heritability estimate of 0.49 was computed. Copyright © 1963. American Society of Animal Science . Copyright 1963 by American Society of Animal Science