Influence of Sulfur Amino Acids on Copper Toxicity in Chicks

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Abstract
These experiments were conducted to investigate the effect of level of sulfur amino acids in the diet on response of chicks to high dietary copper. Adding 500 or 750 ppm copper to a diet deficient or just adequate in sulfur amino acids for chicks significantly reduced growth rate and efficiency of food utilization. Adding 0.4% D,L-methionine to the diet prevented both the reduced growth rate and efficiency of food utilization resulting from 500 ppm added copper. Reduction in food efficiency but not growth caused by 750 ppm copper also was prevented by 0.4% methionine. Hepatic copper levels were significantly elevated in chicks fed copper levels of 500 and 750 ppm but 0.4% added methionine significantly reduced the increase. In a second experiment, adding 0.4% D,L-methionine or 0.332% L-cystine to a diet adequate in sulfur amino acids significantly counteracted the growth depression caused by 500 ppm copper. Significant elevation in copper levels of blood plasma and spleen were completely counteracted and elevation of copper levels in liver and bile were significantly reduced by extra dietary sulfur amino acids. Copper levels in the kidney were not significantly affected by any dietary treatment. Sodium sulfate partially counteracted the copper toxicity. The results demonstrate a protective effect of sulfur amino acids against copper toxicity in chicks.