Requirement of Sulfur-Amino Acid for Starting Chicks

Abstract

The experiments reported in this paper were originally designed to find out the adequate level of supplemental methionine to the basal diets used for the various research works in this laboratory. However, the conclusions obtained by these experiments may be applicable to the practical formula feed.Three types of basal diets were used in these experiments, which were shown with the main protein source in the diet, such as soybean meal diet, casein diet and amino acid diet. Parts of L-glutamic acid in these basal diets were replaced by DL-methionine in experimental diets. The contents of methionine and cystine in the basal diets were determined micro-biologically, using Leuc. mesenteroides P60 and Leuc. citrovorum 8081, respectively.Soybean meal diet was composed with 43.3% of cornstarch, 44.0% of soybean meal, 4.3% of soybean oil, 0.4%, of L-glutamic acid, 6.0% of minerals and 2.0% of vitamins. Casein diet was composed with 53.0% of cornstarch, 18.0% of casein, 10.0% of gelatine, 8.0% of soybean oil, 0.5% of L-glutamic acid, 1.0% of L-arginine, 0.5% of glycine, 6.0% of minerals and 3.0% of vitamins. Amino acid diet was composed with 49.39% of cornstarch, 31.61% of mixture of crystalline amino acids including 12.0% of L-glutamic acid, 8.0% of soybean oil, 6.0% of minerals, 3.0% of vitamins and 2.0% cellulose.Body weight gain and feed efficiency for two to three weeks of White Leghorn male chicks fed a diet containing 0.66% of sulfur amino acids, i.e. methionine+cystine, were almost equal to those of chicks fed diets containing 0.86% of sulfur amino acids. Linear relationship was observed between body weight gain and logarithm of dietary level of sulfur amino acids as shown in Fig. 1, when the dietary level was less than 0.66%. The sulfur amino acids level at the maximum body weight gain was calculated from the regression equation and treated as the optimum sulfur amino acids level, which were 0.65, 0.64, 0.65 and 0.69%, i.e. 0.66% in average.Considering the fiducial limits of the data and the results of feeding experiments with practical formula feed, it is suggested that the adequate level of sulfur amino acids in the diet containing about 20% of protein and sufficient amount of vitamins and other minor nutrients is 0.7% for starting White Leghorn chicks, instead of 0.8% recommended hitherto.