Relaxed Selection in Commercial Crosses of Poultry

Abstract

Comparison was made during an eight and one-half month laying period between three commercial crosses (strains) of poultry and an advanced generation (relaxed selection) population in each strain. The strains differed significantly in egg production, body weight, and egg weight but not in mortality. Relaxed selection resulted in a significant (13%) decrease in egg production and a decrease in body weight (2.8%), but no change in egg weight or mortality over strains. Two strains decreased in egg and body weight due to relaxation of selection while one strain increased in both traits resulting in significant interactions between strains and relaxation of selection for these two traits. The differences in egg production between selected and relaxed lines were primarily due to reduced rate of lay in the relaxed lines. Differences in egg prdouction between strains were due to differences in both rate of lay and age at maturity.