Selection for Body Weight at Eight Weeks of Age

BODY weight at 8 weeks of age is a quantitative characteristic influenced by complex physiological mechanisms. Asmundson and Lerner (1933) demonstrated that inherited differences in body growth were influenced by multiple genetic factors. Jaap and Morris (1937) attempted to quantitatively determine the relative importance of several sources of variation on 8-week weight. In recent years many estimates of heritability have been reported for the body weight of chickens. A summary of 176 published heritability estimates of body weight obtained for chickens 6 to 12 weeks of age is presented in Figure 1. The median heritability was .41 with an inter-quartile range of .29 to .54. This would indicate that, in most of the populations studied, body weight at these ages had a moderate to high heritability. Although the overall range of the estimates given in Figure 1 may appear wide it should be remembered that several methods of estimations were …