Estimates of genetic parameters relevant in selection for certain aspects of egg quality

Abstract

Thick albumen quality of eggs laid by pullets at the approximate ages of 34 and 64 weeks was measured both for fresh eggs and for eggs stored under reasonably uniform conditions for a period of 14 days. Subsequent analyses provided estimates of heritability of these various traits as well as genetic correlations between them. Heritability was high in all cases except for the 64-weeks measurements on stored eggs. Theoretically, selection based on 34-weeks measurements of albumen quality of fresh eggs should be equally as effective, per generation, as direct selection in improving 64weeks fresh quality. Furthermore, this indirect selection is more effective than direct selection in improving the quality of stored eggs, at both 34 and 64 weeks of age.

The heritability of egg specific gravity (used as an indicator of shell thickness) is of intermediate to high value for estimates made both early and late in the pullet year. The genetic correlation between the early and late measurements is high, and selection based on the early measurement should be almost as effective (when assessed per generation) as on the late measurement in causing genetic improvement in late shell quality.

All quality traits examined showed positive genetic relationship with each other, although many of the correlations are of low value. The only serious genetic antagonism disclosed was between each of the two assessments of shell thickness and total egg production. There was no evidence of genetic antagonism between albumen quality and total egg production.