Selenium Deficiency and Transsulfuration in the Chick

Abstract

Experiments were conducted to investigate the effect of selenium (Se) deficiency on the efficiency of cysteine formation from methionine (Met) in three strains of chickens. Hubbard, Leghorn, or crossbred (New Hampshire × Columbian) chicks were fed a crystalline amino acid diet that was fortified with both vitamin E and ethoxyquin but was essentially devoid of Se. The sulfur-containing amino acid (SAA) requirement was provided as equal quantities of Met and cystine (Cys-Cys) or as an isosulfurous level of Met alone. When fed diets unsupplemented with Se, all chicks exhibited depressed growth and markedly reduced blood glutathione peroxidase (SeGSH-Px) activities. SAA source had no effect on SeGSH-Px activity. Source of SAA also had no effect on growth rate of Leghorn or crossbred chicks, regardless of Se status. Se-deficient Hubbard chicks, on the other hand, gained faster and more efficiently when fed the Met-Cys-Cys combination than when fed an isosulfurous level of Met alone. Plasma concentrations of Cys-Cys and cystathionine were reduced in Se-deficient chicks of all strains. Homocystine was detected only in plasma of Hubbard chicks fed Se-adequate diets containing Met as the source of SAA. These findings support the view that transsulfuration efficiency may be impaired by Se deficiency in some strains of chickens.