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Evaluating Relationships among Immature Measures of Size, Shape and Performance of Beef Bulls. III. The Relationships between Post-Weaning Test Performance and Size and Shape at Twelve Months^{1, 2,}

University of Arkansas, Fayetteville 72701 and U.S. Department of Agriculture, Knoxville, Tennessee

Abstract

TEN body measures, including weight, were taken on 267 Hereford (H) and 283 Angus (A) bulls at 12 months of age. The genetic and phenotypic correlations (r_G and r_P) between the individual measures and four feedlot traits including test gain, feed consumed (FCONS), feed conversion (FCONV) and final test weight (FWT) were discussed. The 10 body measures were also used in a principal components analysis for each breed group. The principal components explained the covariance structure among these 10 body measures and the various components provided a means of evaluating bulls according to size and shape. The r_G and r_P between several principal components from each group and the four feedlot traits were considered as measures of the relationship of size and shape to test performance.

The r_G between individual measures at 12 months and measures of feedlot performance of H and A bulls in the feedlot were generally large and positive, with several of the A correlations being smaller than those of H bulls. The r_G between body measures and FCONV were different for the groups. Genes with a positive effect on the body measures improved FCONV of H bulls but had an adverse effect on FCONV of A bulls. The r_P were moderate, positive and very similar for all test traits except FCONV which were negative but sufficiently small to be of little use.

¹ Published with the approval of the Director of the Arkansas Agricultural Experiment Station.

² This study supported in part by a grant from Agricultural Research Service, U.S. Department of Agriculture.

³ Present address, Bovine International, Dallas, Texas.

⁴ Department of Animal Sciences, University of Arkansas, Fayetteville.

⁵ Animal Science Research Division, A.R.S., University of Tennessee, Knoxville.