Chicks were fed mixtures of methionine, cystine, and the calcium salt of the hydroxy analogue of methionine (MHA) in a diet based on a mixture of amino acids. Rate of gain with the basic amino acid diet containing a mixture of methionine and cystine was about 90% of the rate noted with a practical type diet. Efficacy of MHA depended on its level in the diet and on the levels of methionine and cystine fed with it. It was least effective when fed as the only sulfur amino acid or when fed with cystine. When fed with methionine it had intermediate value and was most efficacious when fed with a mixture of methionine and cystine. Essentially it was fully effective when it provided 25% of the sulfur amino acids with the remainder as equal parts of methionine and cystine. Replacing part of the cystine in a mixture of cystine and MHA with methionine resulted in a marked improvement in performance with L-methionine being slightly more effective than D-methionine.
The relative values of the calcium salt of the hydroxy analogue of methionine (MHA) and L-methionine were studied in chick feeding tests with five practical type diets deficient in the sulfur amino acids. Performance was improved with the addition of either substance to each of the five diets. Methionine was slightly more effective at low levels of addition to the four diets primarily deficient in methionine. The two supplements were equally effective in one diet based on corn, soybean, and meat and bone meals, a diet with a wider methionine/cystine ratio. Both the practical and highly purified amino acid diets thus showed similar differences in efficacy of the two products as the methionine/cystine ratio of the diet changed. Methionine also was more effective than MHA in overcoming the deleterious effects produced by the addition of ethionine to a practical type diet.
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