Assay for estimating the potency of various methionine-active sources

A number of experiments were conducted to verify the sensitivity of a low protein (15%) soybean diet for assaying methionine (Met) activity. Although a good response in weight gain and feed:gain ratio was obtained with the addition of supplemental Met to the basal diet, an inconsistent response was obtained when the efficacies of DL-Met and liquid methionine hydroxy analogue (MHA were tested). The addition of nonessential amino acids produced a variable response when added to diets containing MHA, with no difference in the response to aspartic acid or a glycine/glutamic acid mix as nitrogen sources. The addition of glycine to diets supplemented with DL-Met resulted in improved performance with the highest level of Met supplementation, thus suggesting that glycine may be alleviating some deficiency in the high supplemental Met diet. Based on the results of several experiments, MHA was judged to be less efficient than DL-Met on a weight basis.