Combined Animal, Dairy, and Poultry Extension Workshop

other energy depots can be forced, however, genetic associations may remain when phenotypic regression is used. Heritability estimates for phenotypic residual feed intake have been moderate, ranging from 0.26 to 0.43. Genetic correlations of phenotypic residual feed intake with feed intake have been highly positive, suggesting that improvement would produce the correlated response of decreasing feed intake. Residual feed intake estimated by genetic regression results in zero genetic correlation with its predictors thus alleviating concerns over long term antagonistic response in increased mature size and maintenance requirements. The genetic regression approach requires knowledge of genetic covariances of feed intake with growth rate and weight. Cost of individual feed intake measurement on potential replacements will be a consideration for implementation of national cattle evaluations for efficiency of feed utilization. These costs must be compared to expected and, if possible, realized rates of genetic progress and associated reductions in feed input requirements.