Effects of Deviations from Normality on Selection Intensities for Shell Deformation and Egg Weight in Chickens

Distributions of egg weight and egg deformation values of 10,548 eggs, obtained from 530 pullets, were examined. The deviations from normality based on mean values of all eggs from individual pullets over the experimental period were small relative to the estimates obtained when all 10,548 values were used. The effect of these deviations from normality on selection intensities was studied when 5 to 95% of the pullets were hypothetically retained for reproduction. Distribution of both egg weight and deformation using individual data showed considerable departure from presumed normal distribution in the form of positive skewness and positive kurtosis. The nonnormality of distribution tended to over- or underestimate the selection intensities, depending upon the fraction saved and type and extent of deviations from normality.