ABSTRACT
The average weight of eggs produced by selectively bred strains of hens is in the vicinity of 60 g. The variability is dependent on the breed, environmental conditions, size of the egg, and rate of production. The shell shape and weight of hens' eggs are dependent on heredity, age of the bird, season of the year, and diet. Most hens' eggs destined for market have an oval shape. Marion et al. reported mean total solids contents of 11.8 and 11.3% for two flocks over a 1-year production period. The eggshell is made up for the most part of a matrix consisting of interwoven protein fibers and spherical masses, and interstitial calcite or calcium carbonate crystals, in the proportion of about 1:50. The elemental composition of eggshell has been reported by Romanoff and Romanoff to be 98.2% calcium, 0.9% magnesium, and 0.9% phosphorus. For eggs of New Hampshire pullets, the mantle thickness can be as high as 0.172 µm.
