Physical and Chemical Properties of Eggs as Affected by Breeding and Age of Hens

RECENT reports (Cunningham et al, 1960; Marion et al., 1964, 1965; Kline et al., 1965) contain reviews of research dealing with the influence of breeding and/or age of laying hens on egg size and the relative proportions of shell, yolk and albumen in eggs. Generally, these reports support the conclusion that egg size can be controlled by breeding, in addition to being influenced by age of the laying hen. Proportions of egg components appear to be amendable by selective breeding, but are greatly influenced by layer age. The percentages of shell and albumen decrease during the first year of lay with an accompanying increase in yolk percentage. The influence of breeding on the chemical composition of egg contents has also been studied. Protein and moisture levels of eggs were shown to differ in different stocks of layers (Cotterill and Winter, 1954; May and Stadelman, 1960). Lipid and fatty acid …