Availability of oxidized sulfur amino acids for the growing chick

In four trials, experimental diets were fed to one week old broiler cockerels for a period of 14 days to compare the availability of oxidized sulfur amino acids to DL-methionine on an equimolar basis. The data were analyzed by the slope-ratio technique. Chick weight gain per unit feed consumed was the dependent variable and dietary level of supplemental amino acid was the independent variable. There was no significant (P=.05) differences in availability of DL-, L-, and D-methionine. D-, DL-, and L-methionine sulfoxide were 52, 59 and 77%, respectively, as available as DL-methionine. The differences in availability between the three sulfoxides and DL-methionine were significant. Both DL- and D-methionine sulfoxide were significantly less available than L-methionine sulfoxide. No response was obtained from L-cysteic acid or DL-methionine sulfone.