Sulphur is a component of the animo acids methionine, cysteine and cystine; the B-vitamins, thiamin and biotin; as well as a number of the organic compounds. Sulphate, a component of sulphated mucopolysaccarides, also functions in certain detoxification reactions. All sulphur-containing compounds, with the exception of biotin and thiamin, can be synthesized from methionine. Ruminal microorganisms are capable of synthesizing all required organic sulphur-containing compounds from inorganic sulphur. Sulphur is also required by ruminal microorganisms for their growth and normal cellular metabolism.
Most rumen bacteria can synthesize the sulphur-containing amino acids from sulfide.Sulfide can be absorbed from the rumen and oxidized by tissues to sulphate, a less toxic form of sulphur. Sulphur in feedstuffs is largely a component of protein. Dietary sulphur requirements may be higher when diets high in rumen bypass protein are fed b ec ause of sulp hur ’s limitation for o p tima l r uminal fe rmentatio n. Sulp hur supplementation may be needed when urea or other nonprotein nitrogen sources replace natural preformed protein. Mature forages, forages grown in sulphur-deficient soils, corn silage can be low in sulphur. Sorghum forages seem inherently low in sulphur relative to other forages.
Sulphur can be supplemented in ruminant diets as potassium sulphate magnesium sulphate > sodium sulphate > copper sulphate > ammonium sulphate > calcium sulphate or elemental sulphur. Based on in-vitro microbial protein synthesis, sulphur availability to ruminal microorganisms has been ranked from most to least available sources as L- methionine, calcium sulphate, ammonium sulphate, DL-methionine, sodium sulphate, sodium sulfide, elemental sulphur and methionine hydroxy analog.