Sulfur Toxicity in Feedlot Cattle

Introduction: Sulfur is an important component of many functions in the body and is an essential nutrient for beef cattle. It is an important part of the amino acids methionine, cysteine, and cystine. The B-vitamins thiamine and biotin also contain sulfur. Rumen microbes require sulfur for their normal growth and metabolism. A large portion of the sulfur found in typical feedlot diets is a component of the natural protein and most practical diets are adequate in sulfur (NRC, 1996). However, feeding diets high in non-protein nitrogen or high in rumen undegradable intake protein may reduce the amount of sulfur available for rumen microorganisms thus increasing the need for supplemental sulfur. The requirement for sulfur as stated by the National Research Council is 0.15% of diet dry matter and maximum tolerable level is listed as 0.40% of diet dry matter (NRC, 1996).