Calories, Water, Lipid and Yolk in Avian Eggs

Abstract

The contents of fresh eggs of altricial, semi-altricial, semi-precocial and precocial birds were compared with values for yolk content gathered from the literature. The continuum of developmental maturity at hatching from altricial to precocial eggs is correlated with an increase in yolk, solids and caloric contents (per gram wet mass), and with a decrease in water content. The proportion of lipid in dry matter and caloric content per gram dry mass does not vary significantly among the 4 developmental groups. The progressively higher caloric content on a wet mass basis with increasing precocity is a result of a larger solid content and lower water content, rather than variation in caloric value of the dry matter itself. Comparison of values within the same developmental group discloses no significant correlation between relative yolk content and egg mass. The total amount of calories in eggs is more importantly determined by egg mass than by yolk content.