A chick assay for availability of lysine in wheat

A chick growth assay was developed to estimate the availability of lysine in cereal grains. Amino acids were supplied in the basal assay diet by hydrolyzed-feather meal, gelatin, and crystalline amino acids. Dietary nitrogen levels were equalized for all assay diets by adjustment of glutamic acid content, and dietary energy levels were equalized by adjustment of the proportions of corn starch, corn oil, and cellulose. The assay method was tested for validity with two wheat cultivars, using dietary lysine level or lysine intake as the independent variable and weight gain or carcass nitrogen gain as the dependent variable. Taking lysine level as the independent variable did not satisfy statistical tests for validity of the assay procedure. Availability of lysine determined by the selected method of regression of weight gain on lysine intake was .79 (with 95% fiducial limits of .94 and .66) and .76 (.87 and .66) for Manitou and Pitic cultivars, respectively.