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Economic Importance of Traits and Selection Indexes for Beef Cattle

Colorado Agricultural Experiment Station,¹ Fort Collins

Abstract

A study was made to determine the relative economic importance of weaning weight and grade, daily gain, days to finish, slaughter grade, feed per pound of gain, and cow maintenance costs in determining net income in a calf raising and feeding operation. A selection index designed to attain the maximum genetic progress toward increasing net income per hundred-weight of the finished product was developed. Price and cost data were applied to 118 Hereford steer calves, bred and fed by the Colorado Agricultural Experiment Station, to obtain individual net income estimates. The net income estimates were divided by each 100 lb. slaughter weight to place net income in dollars on the basis of one hundred pounds slaughter weight.

Multiple correlation studies, using net income per hundredweight as the dependent variable, indicated that weaning weight was the most important trait affecting net income. Weaning grade and days to finish did not add to the information provided by weaning weight alone. Weaning weight and daily gain gave the highest multiple correlation with net income per hundredweight of any combination of two independent variables. Other important traits, as indicated by the standard partial regression coefficients, were slaughter grade, feed per pound gain and 18-month weight of dam.

Heritability estimates were computed for weaning weight W; daily gain, R; days to finish, F; and feed per pound gain, E. The standard partial regression coefficients, obtained when these four traits were used as the independent variables, were used as the estimate of relative economic importance. The index containing the four variables was I=+.58 W+18.64 R–.73 F–5.87 E. Because of the greater standard deviation, weaning weight was over twice as important as days to finish in determining the index value of the individual and feed pound gain and daily gain were least important. This study indicated that weaning weight alone was an accurate basis for selecting for increased net income in these Hereford calves. Another simple index apparently of considerable accuracy would be I₈=W+72G.

¹ Approved for publication as scientific paper SS-493 of the Colorado Agricultural Experiment Station. It is included in the Western Regional Project W-1 in cooperation with the A. P. H. Branch, U.S.D.A.