BEEF BULL GROWTH RATE EVALUATION PROCEDURES

Abstract

Procedures for estimating the breeding value for average daily gain of beef bulls across breed and across test groups are described. The estimates are best linear unbiased predictions taking inb account breed, test-group, paternal half-sibs and heritability. Breed differences based on canadian test stations indicate that Angus gain approximately .05 kg/day less, Shorthorn about the same and charolais .25 kg/day more than Hereford, with these differences fairly similar for all provinces. The use of evaluations across groups is compared with evaluations within group, considering the differences between large sample and small sample selection and the accuracy of estimating breeding values across groups relative to within groups. Expected genetic progress was found to be similar for across- and within-group selection procedures for fixed tested population size with an advantage for selection across groups for groups with many sires, especially for small numbers of bulls selected. Evaluations across groups can be more flexible, allowing for selection both within and across groups.