The progeny testing of dairy bulls—a comparison of tests on father and son

Abstract

1. A comparison has been made of the progenytest figures for father and son in the Friesian breed.2. There was a significant regression of contemporary comparison of son on contemporary comparison of father (0·22) and on r.b.v. of father (16·4 lb. per unit of r.b.v.), though both figures were about one-quarter lower than expected. The observed figures were consistent with a heritability of heifer yield of 0·19. The regression of contemporary comparison of son on the average production of the herds in which his half-sibs were milked was small and not significantly different from zero.3. For fat content, the regression of son's daughter average on father's daughter average was 0·32, in agreement with expectation.4. A less-detailed analysis for the Ayrshire breed on the above points gave essentially similar results.5. The possible extent of selection on the basis of progeny-test results was looked into. For yield, the selection was small, leading to a probable improvement of 1–2 gal. a year. For fat content, the probable increase was 0·01% a year.6. A method is described for evaluating the progeny test of a son in relation to his father's own progeny-test results, which can serve as a method of combining the progeny-test figures from different bulls.