Selection for Body Weight at Eight Weeks of Age

HERITABILITY is a statistic which describes a certain population in terms of observed phenotypic variance due to differences between individuals in their heredity (Lush, 1948). Various methods for estimating heritability have been developed and their advantages and disadvantages were discussed by Lerner (1950, 1958) and Falconer (1960). A reliable measure of additive gene action may be obtained by dividing the difference between the means of two lines selected in opposite directions by the cumulative selection differential. The use of random mating control populations enables the refinement of being able to calculate the heritability in both upward and downward directions and thereby minimize influences of asymmetry in the response of the divergently selected lines. Falconer (1953) has also shown that a reliable method for measuring additive gene action in two-way selection experiments is by the regression of the response on the cumulative selection differential. Harvey and Bearden (1962) presented procedures for …