Effect of storage and layer age on quality of eggs from two lines of hens

Eggs from ISA-White and ISA-Brown hens between 28 and 59 wk of age were sto red for up to 10 d to produce a sample of 5,763 eggs differing in the three major determinants of albumen quality. Eggs from ISA-Brown hens were large r and had less yolk, more albumen, and a greater percentage of shell than t hose from ISA-White hens. Egg size increased with increasing age of the hen , although more for the ISA-White hens than the ISA-Brown hens, and the yol k increased more in size than did the shell and albumen. During storage, al bumen weight decreased and yolk weight increased slightly. The height of th e inner thick albumen of eggs from ISA-White hens was greater than that of eggs from ISA-Brown hens, and it decreased as the hen age increased and wit h increasing time in storage. The pH of the albumen was not different betwe en strains, and the effect of hen age was small, but it increased with time in storage. Regression coefficients of the height of the inner thick album en on the weight of the egg were between -0.058 and 0.102, showing that the fixed regression of 0.05-mm albumen height per gram of egg implied by the Haugh unit is wrong. The statistical association between albumen pH and egg weight was very low. If albumen quality is being used as a measure of fres hness, then the albumen height is biased by the strain and age of hen, wher eas the albumen pH is not.