A Selection Strategy to Keep Fertility and Hatchability at High Levels

Abstract

It is difficult for breeders to apply sufficient selection pressure to the key characters required for commercial success because there are so many economic traits to be considered. Fertility and hatchability are usually at high levels (over 90% for fertility and 85% for hatchability) unless there are severe problems. Fitness characters of several species have been shown to have low, asymmetrical heritabilities (Frankham, 1990). Also, there are many examples of major genes affecting fitness (Merat, 1990). In two studies, an experiment using Drosophila (Frankham et al., 1988) and a simulation study (Li and James, 1992), it was concluded that culling on low fitness can reduce or eliminate fitness loss without substantial reduction in response for other traits under selection.