THE DETERMINATION OF THE OPTIMUM RATIO BETWEEN THE ESSENTIAL AMINO-ACIDS IN LAYING HEN DIETS

From the reduction in nitrogen retention after partial dietary deletion of individual essential amino acids the ideal ratio between methionine, methionine plus cystine, leucine, valine, phenylalanine and phenylalanine plus tyrosine was determined. Light, white laying hens (41 and 26 weeks old, nine hens each per experimental treatment) were given in two experiments eight diets for 54 days each. In both trials one diet (positive control = K+) contained all essential amino acids at the requirement level, while in sir, further diets, compared to the positive control (K+), the concentrations of individual amino acids (methionine (diet -Met), methionine plus cystine (diet -M+C), leucine (diet -Leu), valine (diet -Val), phenylalanine (diet -Phe), phenylalanine plus tyrosine (diet -P+T)) were partially reduced. This reduction normally was as high as 25%, but was only 15% in diets -Leu and -Phe in the second experiment. In an eight diet (negative control = K-) the concentrations of all essential amino acids reached only 75% of their level in the positive control (K+). The basal diet (K+) in the second trial contained 31% of its protein in form of free amino acids, while this parr reached 43% in the basal diet (K+) of experiment one. Partial deletion of individual dietary amino acids mostly caused a reduction in egg production, feed consumption and nitrogen retention as well as a poorer feed conversion efficiency and a poorer development of body mass of hens. Excluded from this were the treatments with lower dietary concentration of methionine plus cystine (diet -M+C) in both trials and the treatment with a dietary reduction of methionine (diet -Met) in the second trial, which therefore could not be involved in the calculation of the optimum amino acid pattern. From the results of total nitrogen retention of both experiments an optimum ratio from methionine:leucine:valine:phenylalanine:phenylalanine plus tyrosine like 100:215:146:133:243 was derived. Combining this pattern with the one of an earlier work (KIRCHGESSNER et al., 1995) led to an ideal pattern of lysine:methionine:threonine:tryptophan:leucine:isoleucine:valine:phenylalanine:phenylalanine plus tyrosine:arginine like 100:44:76:16:94:76:64:58:107:82. These results were compared to egg protein and to some other recommendations on the amino acid requirements, differences and possible influences of the experimental method used were discussed.