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Selection Indexes for Efficiency of Beef Production¹

University of Nebraska, Lincoln , U. S. Department of Agriculture and and University of Illinois, Urbana

Abstract

Measures of growth rate, feed consumption, carcass composition and quality grade were available on 480 beef calves. Measures of net merit expressing differences in profit were computed on a total and postweaning basis as the value of retail product less feed costs. Heritabilities and phenotypic, genetic and environmental correlations among the traits were computed. The heritability was 0.24 for percent retail product and 0.65 for growth rate of retail product. Percent retail product was genetically correlated positively with weaning weight (0.09) and weight of retail product (0.15) and negatively with postweaning gain (–.45), final weight (–.25) and feed consumption (–.20). Percent retail product had large negative genetic correlations with fat thickness over the rib (–.77) and quality grade (–.85). Fat had a positive genetic relation (0.56) with quality grade.

Thirteen selection indexes predicting total and postweaning net merit were computed using combinations of traits or single traits. For total net merit feed consumption could be omitted from an index containing measures of growth rate with no loss of efficiency of selection. Deleting fat as an indicator of composition resulted in a loss of efficiency of about 8%. This represents a maximum compared to the use of live animal measures of fat, since carcass measured fat was used. Selecting for final weight alone is expected to be 90% as effective as an index combining preweaning and postweaning gain with feed consumption and an accurate measure of fat thickness for selection for total net merit. Selecting for weaning weight alone should be 80% as effective as the best index and can be recommended when postweaning information is not available.

Selection for final weight is simpler and more economical than using an index containing in addition feed consumption and an indicator of carcass composition, and it should be nearly as efficient for changing net merit. Therefore, selection for adjusted final weight should be a recommended procedure for the beef industry. When an accurate and economical measure of live animal fat is available, it can be combined with final weight in an index with some increase in efficiency of selection for net merit expected. Use of this index should result in developing cattle with slightly less appetite, final weight and grade and slightly higher percent retail product than selecting for final weight alone.

¹ Published with the approval of the Director as Paper No. 1658, Journal Series, Nebraska Agricultural Experiment Station. Contribution from North Central Regional Project NC-1, Improvement of Beef Cattle through Breeding Methods.

² Beef Cattle Research Branch, Animal Husbandry Research Division, Agricultural Research Service, U.S.D.A., Lincoln, Nebraska.

³ Department of Animal Science, University of Illinois, Urbana.