Relative Contributions of Genetics and Environment to Turkey Improvement

Abstract

PHENOTYPIC changes (improvements) which occur over a period of years may be subdivided into a genetic and an environmental component through the use of randombred control populations. Recently, randombred control populations have been used in an attempt to hold the genetics constant and measure environmental change over years (Kinney et al., 1968; Merritt, 1968; and Kinney and Lowe, 1968). Genetic changes in a control flock may result from random changes of gene frequency due to genetic sampling or “genetic drift” and directional changes due to natural selection (Gowe et al., 1959). With additive gene action, the expected drift variance of the mean is equal to 2F σg2 where F is the inbreeding coefficient and σg2 is the additive genetic variance in the character concerned. This is equal to σg2/Ne drift variance per generation. Ne is the effective number of parents (Gowe et al., 1959). Thus, from the above, the larger…