Relations of yolk, albumen and egg weight in inbred lines of brown leghorns

Abstract

1. The relations of yolk, albumen and egg weight were studied in seven inbred lines of Brown Leghorns and reciprocal crosses of two of these lines. 2. In all the lines the eggs produced by hens had a bigger proportion of yolk than those produced by pullets. 3. Besides changes in both components accompanying differences in egg size the line means for albumen weight still differ significantly after adjustment is made for its covariance with yolk weight. This independent variation leads to differences in the yolk-albumen ratio of the hens. 4. Within the lines there is a significant negative association between egg size and the yolk/albumen ratio. 5. The wide differences in egg size, dividing the pure lines into two groups characterized by large and small eggs respectively, resulted from a marked decrease in the amount of albumen in the eggs of the latter group. Yolk weights, on the other hand, could be ranked in a fairly regular series with adjacent lines differing by 2 g. or less. 6. There is some source of variation in the yolk/ albumen ratio for line means which is not accounted for by differences in egg size.