16 - Sulfur bioavailability

Abstract

Sulfur is distributed widely in nature as a component of proteins and numerous other organic compounds and, consequently, it has many structural and regulatory functions in common with nitrogen. Utilization of absorbed inorganic sulfur has been demonstrated in avian species and probably occurs in most other species. The predominant need for the element, however, is in the form of sulfur-bearing amino acids which must be provided preformed for the nonruminant or either provided preformed or synthesized by ruminal microflora for the ruminant. True absorption of sulfur in dairy steers fed a concentrate containing urea (0.21% sulfur) and corn silage (0.20% sulfur) was 68%. Supplementation of lactating dairy cows with sulfur as sodium sulfate, methionine hydroxy analog, or dynamate increased apparent and true sulfur absorption. Apparent absorption of sulfur was similar when either sodium or calcium sulfates was supplemented to lactating dairy cattle. Dietary proteins with their sulfur-containing amino acids provide a major dietary source of sulfur for animals. Interactions among mineral elements including copper, molybdenum, and sulfur and those involving sulfur and selenium influence the utilization of sulfur. Factors that change the population of ruminal microflora may also affect the availability of inorganic sulfur. Sulfur is a more critical nutrient for ruminants than nonruminants from the standpoint of potential deficiency. Organic forms including the isomers of methionine and methionine hydroxy analog have provided sulfur equal in availability to that in sodium sulfate. Elemental sulfur and sodium sulfate were not utilized when tested in both cattle and sheep.