Effect of Dietary Glycine on Reduced Performance by Deficient and Excessive Methionine in Broilers

Abstract

To clarify the alleviatory effect of dietary glycine on reduced performance caused by deficient and excessive methionine, two experiments were conducted. In Experiment 1, the adequate methionine level for the maximum performance of broilers was determined by supplementing a cornsoybean meal diet with a graded levels of methionine. In Experiment 2, the effect of glycine on the depressed performance of broilers caused by methionine deficiency and excess was studied.
In experiment 1, the dietary methionine level for the maximum performance was estimated to be at 0.47%, and that for 70% of the maximum performance at 0.26 and 1.56% of diet, respectively. Therefore, in Experiment 2, the 0.26, 0.46 and 1.56% methionine diets with or without 0.60% glycine were prepared, and designated as the deficient, adequate and excess diets, respectively. Reduction of performance caused by excessive methionine was restored to 88% of the growth on the adequate diet, but that caused by methionine deficiency was not alleviated by adding glycine. Abdominal fat contents on the methionine excess diet were less than those on the deficient diet, although there were no differences in performance. Reduced abdominal fat content to 47% of the adequate diet was recovered to 67% by adding glycine. Plasma methionine concentration increased rapidly with increasing dietary methionine levels, and reduced by adding glycine. Plasma glycine, threonine and serine concentrations were not reduced in chicks fed the methionine excess diet.