Evidence of a Hereditary Factor Affecting the Chick's Response to Uncomplicated Selenium Deficiency

ABSTRACT Experiments were conducted to determine whether a hereditary factor accounted for part of the variation observed in the growth responses of young chicks to uncomplicated selenium (Se) deficiency. Results showed that such a factor influenced the growth of chicks fed a Se-deficient diet. Those chicks most susceptible (SUS) to the growth depressing effects of Se-deficiency oxidized '4 CH3-methionine to 1 4 C0 2 at a greater rate when fed the Se-deficient diet than did chicks that appeared refractory (REF) (i.e., grew at near normal rates) to Se-deficiency. When diets were supplemented with Se, both lines exhibited equivalent rates of 14CH3-methio-nine oxidation. The SUS chicks appeared to have lower levels of free homocystine and cystathio-nine in plasma compared to REF chicks or to Se-supplemented chicks of both lines. These results provide evidence for an impairment in sulfur-amino acid metabolism as the basis of the hereditary effect. (Key words: selenium, methionine, chick