Genetic control of egg quality

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Abstract
Measurements of specific gravity, egg weight and albumen height of eggs from three consecutive trap days were taken at approximately 225, 350 and 450 d of age, for three years, from three strains of the White Leghorns. Haugh units were calculated for each egg. From these data estimates of genetic parameters were derived. Pooled estimates within the 27 strain‐period‐year subclasses for heritability of single egg records from sire components of variance for specific gravity, egg weight, albumen height and Haugh units were 0.36, 0.48, 0.46 and 0.45, and repeatability within periods for the four traits were 0.68, 0.74, 0.76 and 0.74 respectively. The intra‐class correlations (repeatabilities) between period‐means of the same hen expressed in standard deviation units for each subclass were 0.58, 0.71, 0.74 and 0.69 respectively. Genetic correlations between adjacent periods were high varying from 0.91 to 0.96 while those between non‐adjacent periods varied from 0.76 to 0.87 for the four traits. It was suggested from the size of these estimates that annual performance for a quality trait could be improved by selecting pullets on the basis of a small number of egg measurements taken at early periods in the laying year.