Effects of amino acid supplementation and methanol treatment on utilization of soy flour by fingerling carp

Abstract

Effects of crystalline amino acid supplementation and methanol treatment on utilization of soy flour by fingerling carp, Cyprinus carpio, were studied in a 4-week feeding trial. Fish fed diets in which 75% of the fish meal was isonitrogenously replaced with methanol-treated or untreated soy flour achieved almost a 350% weight gain in 4 weeks if the test diets were supplemented with essential amino acids to the levels in a fish meal-torula yeast control diet. This is approximately 90% of the value attained by the control group. However, feed efficiency and percentage of protein deposition of the test groups were slightly but significantly lower than those of the control group. Methanol treatment failed to show any effect on perfomance of the carp. Neither essential amino acid supplementation nor methanol treatment of soy flour had any effect on whole body proximate composition of carp. The only significant difference noted in the plasma amino acid levels of carp at 6 h post-feeding was methionine among the dietary treatments. Fish performance was more closely correlated to the amino acid profiles of plasma than those of the diets. Therefore, the former was far superior to the latter for evaluation of protein quality in a diet supplemented with crystalline amino acids.