Distribution of selenium in egg white and yolk after feeding natural and synthetic selenium compounds

Practical diets containing various selenium levels, with and without selenite supplementation, were fed to hens. Eggs were then collected over a 14-day period to determine how quickly changes in dietary selenium affected egg white and yolk selenium. Changes in egg white selenium content were rapid and essentially completed seven days after changing the selenium content of a practical diet. Changes in egg yolk were not yet completed by 14 days. When selenium from practical feedstuffs was fed, the selenium content of dried egg white was about equal to or greater than the selenium content of dried egg yolk. When selenite was fed, the selenium content of dried yolk was higher. Feeding selenomethionine resulted in more selenium in egg white than in egg yolk. Feeding selenocystine resulted in more selenium in egg yolk than egg white, a pattern similar to that from feeding selenite. The data suggest that selenocystine is not incorporated into protein but is metabolized to an inorganic selenium compound.