The Relative Breeding Worth of Full Sisters

THE earlier systematic attempts at the improvement of the productive characters of poultry were based on mass selection, a term used in animal breeding interchangeably with individual selection or selection on the basis of individual performance. The assumption underlying this method is that the individual’s phenotype for the trait in question presents an adequate measure of its genotype for the same trait. A notable experiment to test this assumption for annual egg production was undertaken in 1898 by Gowell whose results were subsequently analyzed by Pearl and Surface (1909). The conclusions reached by them were unfavorable to the original thesis to such a degree that a complete lack of correlation between phenotype and genotype was virtually postulated (see Pearl, 1912, p. 388). As a result the notion that progeny testing, a method whereby the individual’s genetic merit is judged on the basis of the phenotypes of its offspring, is a . . .