Postweaning Weights and Gains of Cattle Raised under Range and Gain Test Environments2

Abstract

Progeny from an outbred Hereford herd maintained under southwest range conditions were evaluated in two diverse environments. All heifer progeny and a random one-half of the bull progeny from each sire group were retained on the ranch under range conditions until 2 yr of age. The remainder of the bull calves were placed on 140-d postweaning gain test in Tucson. Traits evaluated on the gain test (and heritability estimates ± SE) were initial weight on test (.19 ± .20), final weight off test (.52 ± .24), final body condition score (.07 ± .18) and 140-d gain (.47 ± .23). Traits evaluated on heifer progeny under range conditions (and heritability estimates ± SE) were weights and condition scores at 12 (.42 ± .18 and .02 ± .11), 20 (.29 ± .21 and .17 ± .20) and 24 mo (.24 ± .22 and .07 ± .19), and daily gains from 8 to 12 (.15 ± .14), 12 to 20 (.33 ± .22) 12 to 24 (.17 ± .21) and 20 to 24 mo (.08 ± .21). Gains from 8 to 12 and 20 to 24 mo were negative. Genetic correlations among weights and gains within environments were generally positive. Environmental and phenotypic correlations in the gain test environment also were positive, but were variable in the range environment. The sire × environment interactions were not important sources of variation among weights under range conditions and weights and gain on the gain test. The interactions were significant for gain traits under range conditions when cattle lost or minimally gained weight and for both final weight and 140-d gain on the gain test. Product-moment and rank correlations among estimated breeding values in both environments indicated a low association of sire rankings in the different environments. Selection of heifers for weights under range conditions at 12 or 20 mo should result in favorable indirect responses in weights and gains of half-sib bulls in the gain test environment.