Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science


An improvement in the quality of beef and in production methods will raise the living standards of both the rancher and consumer. Raising quality can be best accomplished by selecting breeding stock which foster desirable qualities in their offspring in proportion to the economic value of that particular characteristic. The objective of this study was to evaluate various selection device sin relation to the improvement which can be realized through their application. This dissertation examines the effects of such variables as color, condition, and weight on conformation scores and to determine whether or not individual judges differ significantly in these relationships. The data for this study was collected from 184 grade Hereford steers raised by private producers in South Dakota during 1959 and 1960. An analysis was included to examine the effects of such variables as color, condition, and weight, on conformation scores and to determine if individual judges differed significantly in these relationships. The influences of age and weight on line-animal measurements and scores and carcass characteristics were also studied. Zero-order and partial correlations with tests of significance of deviations due to regression were used in these analyses. Genetic and phenotypic parameters estimated by the hierarchal method of analysis were used to formulate 31 selection indices for use in beef cattle populations. The accuracy of each index in predicting the aggregate genetic value of an animal was derived. These indices utilized five production traits: weaning weight, initial conformation, final conformation, post-weaning daily gain, and final weight. Heritability estimates and genetic, environment, and phenotypic correlations were obtained from the paternal half-sib analysis of variance and covariance.

Library of Congress Subject Headings

Beef cattle
Beef cattle -- Breeding


Includes bibliographical references




South Dakota State University