The effect of wheat cultivar, growing environment, and enzyme supplementation on digestibility of amino acids by broilers

Fifty-four samples of wheat, representing duplicate samples of nine varieti es grown in three environments, were included in chick bioassays using rapi dly growing broilers, complete diets, and enzyme supplementation to remove the deleterious effects of non-starch polysaccharides. An insoluble ash mar ker was included in the diets, which allowed calculation of apparent digest ibilities of CP and AA in the grain from analysis of the ileal contents obt ained after sacrifice of the chicks at 17 d of age. The wheat cultivars con tained from 13.5 to 16.8% CP and differed in the percentage of specific AA, with Pro, Glu and Phe making up proportionately larger parts of high CP sa mples than low CP samples. Without enzyme supplementation, the digestibilit y of CP varied from 83 to 88% and that of specific AA from 76 to 94%, deter mined in part by the class and variety of wheat. Xylanase enzyme supplement ation improved the digestibility of protein by an average of 4 %, and reduc ed the differences in digestibility between wheat samples. These results su ggest that variation between wheat samples should be taken into considerati on when formulating broiler feed, especially when formulation is for specif ic AA. Enzyme supplementation may provide a partial alternative to using hi gh-quality protein sources or supplementing with synthetic AA.