Correlations Between Measures of Eggshell Quality or Percentage of Intact Eggs and Various Economic Traits

Abstract

Correlations between various shell quality traits or percentage of eggs remaining intact and economic traits were studied in F1 and F2 populations of White Leghorns. Eggshell quality traits were measured early (42 or 45 wk of age) or late (67 or 68 wk of age) and included specific gravity, nondestructive deformation, compression fracture strength, shell weight, and shell weight per unit surface area. Percentage of eggs remaining intact from oviposition to placement in fiber trays after being washed, candled, and sorted was measured. Economic traits studied included egg production traits, egg traits, and hen traits.All phenotypic correlations between shell quality traits or percentage intact and economic traits were low, being equal to or less than .21. High egg production was associated with low shell quality. However, high egg production from 386 to 497 days was associated with early high percentage intact [(genetic correlation) rg = .38, P<.05] but was not correlated significantly with percentage intact at other ages. The egg traits, Haugh units and blood spots, were not associated with shell quality traits or percentage intact. As for hen traits, high BW at 365 days was associated with high shell weight (rg = .23 and .32, P<.05). Other correlations involving age at first egg, viability, fertility, and hatchability were antagonistic to selection objectives in some instances, but were not significant. It was concluded that the genetic correlations between egg specific gravity or other shell quality traits and economic traits would allow improvement in percentage intact without seriously compromising selection objectives for other traits.