The Effect of Nutrition on the Composition of Eggs ,

Abstract

Variability in the composition of shell eggs due to the composition of the diet fed to the laying hen exists for a number of nutrients. The fat soluble vitamin content of the egg may vary considerably. While vitamin A and its carotenoid precursors may vary several fold, the liver of the hen moderates the flow of vitamin A to egg yolk. Vitamin D may vary widely and limited data suggest considerable variation in vitamin E content. The relative amounts of 18-carbon fatty acids in egg yolk lipid may vary considerably depending upon the nature of dietary fat. Cholesterol content of egg yolk may also be influenced by large amounts of dietary fat, sterols, and drugs.\rAmong the water soluble vitamins, the vitamin B12 content of the egg can vary considerably, dependent upon its level in the hen diet. Folic acid and pantothenic acid levels in the egg also vary somewhat as does the egg content of unidentified factors for growth of the newly hatched turkey poult. Content of most other water soluble vitamins shows minimum variability.\rThe iodine and selenium content of the egg may vary considerably dependent upon the hen’s diet. Iron content of the egg shows minimum variability with dietary change while some variation is possible in other trace elements.\rA consideration of earlier data on shell egg composition with that obtained during the past five years shows that the nutrient composition of the egg has not changed greatly in response to modern industry practices. Some variability can be expected, particularly with regard to egg content of those factors mentioned above. It appears that adequate data are available for most nutrients to permit nutritional labeling of eggs and egg products.