XIX.—Family Selection in Poultry: the Use of Sire and Dam Family Averages in Choosing Male Parents

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Abstract
A typical poultry flock consists of offspring from a number of sires each mated to several dams. In choosing male parents in a selection programme no criterion of individual merit may be available and selection must usually be based on the performance of related females. The present report deals with the theoretical efficiencies of three systems of selection of males(1) on the average performance of the dam family of a male's sisters.(2) on the average performance of the sire family of a male's full- and half-sisters.(3) on a weighted combination of sire family and dam family averages.For traits of low heritability system (2) may offer marked advantages over system (1), the only type of family selection previously investigated. This should prove of importance in flocks where recording facilities are limited. Providing environmental effects can be minimised, efficient selection may be based on the average performance of sire families housed as units without individual recording.The efficiency of system (2) declines with increasing heritability and is also subject to complications introduced by population size. In all cases, however, optimum gains may be obtained on system (3) when both dam family and sire family records are available.