Amino Acid Supplementation of Opaque-2 Corn Diets for Growing Rats

Four trials involving 210 weanling male albino rats were conducted to determine the extent of deficiencies of amino acids in opaque-2 corn and to reevaluate the needs of the growing rat for several of the essential amino acids. The basal diet contained 9.2 to 9.4% protein equivalent and was characterized by a lack of gross excess of any essential amino acid and a ratio of nearly 1:1 of essential-to-nonessential amino acid nitrogen. Excellent daily gain, gain/feed and protein efficiency ratio (nitrogen retention in one trial) were obtained when the diet containing 89.5% oaque-2 corn was supplemented with 0.1% L-isoleucine, 0.18 to 0.35% L-lysine, 0.2% DL-methionine, 0.12% L-phenylalanine, 0.14% L-threonine and 0.08% L-valine. Final dietary levels of 0.36% isoleucine, 0.70% lysine or less, 0.40% methionine + cystine, 0.59 to 0.65% phenylalanine + tyrosine, 0.43% threonine and 0.54% valine appeared to be adequate for the growing rat. These results indicate that currently accepted requirements of the growing rat for isoleucine, lysine, methionine + cystine, phenylalanine + tyrosine and threonine may be slightly excessive.