The Correlated Response of Relative Aggressiveness to Selection for Body Weight and Breast Angle in Chickens

THE associated changes of unselected characteristics in single trait selection experiments are known as correlated responses. When two traits are genetically correlated, a change in the mean genotypic value of the selected characteristic is associated by a concomitant change in the genotypic value of the unselected characteristic. The change is proportional to the genetic correlation between the characteristics and the ratio of the square roots of the genetic variances of the selected and unselected traits. Discussions of the theory of correlated responses and outlines of computational procedures have been given by Lerner (1950) and Falconer (1960). In a double selection experiment, Siegel (1962a) mass selected chickens for high and low body weights and broad and narrow breast angles. The purpose of this paper is to present data on the correlated response of relative aggressiveness during the course of those two-way selection experiments. Seven inbred lines of White…