THE IDEAL RATIO BETWEEN LYSINE, METHIONIN E, THREONINE, TRYPTOPHAN, ISOLEUCINE AND ARGININE IN LAYING-HEN DIETS

The ideal dietary ratio between lysine, methionine, threonine, tryptop han, isoleucine and arginine for laying hens was determined by measuri ng the reduction in nitrogen retention that rakes place when feeding d iets in which the content of one single amino acid was reduced in each diet. A total of eight diets were therefore given to nine light-white hens (28-weeks old) for 54 days. The amino-acid concentrations in one diet (positive control = K+) met the requirements, while, in six diet s, the concentration of a single amino acid (lysine (diet Lys), methio nine (diet Met), threonine (diet Thr), tryptophan (diet Trp), isoleuci ne (diet Ile) and arginine (diet Arg)) was reduced by about 25% relati ve to diet K+. In the eighth diet (negative control = K-), the concent rations of all essential amino acids reached only 75% of the level in diet K+ (positive control). The partial deletion of single amino acids caused a reduction in egg production, feed intake and nitrogen retent ion, as well as a poorer feed conversion and reduced development of bo dy mass in the hens. Lowering amino-acid supply generally decreased th e concentrations of these amino acids in the blood plasma of the hens. The results of total nitrogen retention suggested that the ideal rati o of lysine:methionine: threonine :tryptophan: isoleucine:arginine is 100:44:74:16:76:82. This result is compared to egg protein and some ot her amino-acid recommendations. The advantages and possible sources of error of the method are mentioned.