IMPROVEMENT IN NUTRITIVE QUALITY OF WHEAT-GRAIN PROTEIN BY BREEDING BASED ON REACTION TO LYSINE SUPPLEMENT IN FEEDING TESTS

Results of wheat microfeeding experiment used as model system are repo rted on nutritive quality expressed in weight gain and conversion effi ciency. Whole grains of bread wheat (T. aestivum) varieties, partly im proved for protein (N) content without and with lysine supplement were fed as the only protein source in semi-synthetic diets. Restricted le vel of casein in a diet served also as control. Surplus differences in protein (N) content among selected wheat cultivars without addition o f lysine were not manifested in nutritive effect, only as a trend betw een extremities. Lysine supplement improved the nutritive quality and the feeding parameters of each wheat diet. Responses to consumption ar e however not in consequent correlation with the type order of varieti es according to their protein content and reflect changes from the exp ected nutritive responses based on their close protein content rank. I n case of wheat with the highest protein content weight gain reached t he level of casein feeding /!/ but its protein efficiency ratio was am ong the worst. The conversion of free lysine was worse than that of th e organically bound one. The estimated utilization of methionine was p romoted by addition of lysine. Detected nutritive responses to lysine supplement show that (bio)chemically determined N, amino acid componen ts etc. without in vivo tests are not satisfactory parameters for sele ction of breeding aims in nutrient quality improvement. For the same p urpose it is also proven that instead of gluten whole grain should be used.