Selection Procedures for Poultry Flocks with Many Hatches

Abstract

THE main purpose of the present study was to determine the effect of differences in duration of hatching season upon variation in production traits of chickens. The accuracy of estimating genetic worth of breeding animals and, hence, the efficiency of selection decisions depends among other factors on family size, which in turn depends on the number of hatches and thus on the duration of the hatching season. It is conceivable that an extended hatching season might, because of purely environmental causes or interaction between genotypes and environment, lead to an increase in variation among full sisters. Such added sources of nongenetic variation would tend to counteract the anticipated advantages of large families. Some of the problems pertaining to family size have been discussed by Lerner (1950) and by Lerner and Dempster (1951). In a more recent study King and Henderson (1954) have given quantitative estimates of variation introduced by …