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VetBooks.ir Chapter 35

Sulfur

Jeffery O. Hall

INTRODUCTION In addition to dietary sulfur, other sulfur-containing
compounds can be toxic. Sulfur dioxide gas from indus-
Sulfur is a necessary dietary component that can be toxic
trial waste gas, as well as hydrogen sulfide gas from
at excessive concentrations. Animal bodies are about
manure pits, natural gas production and crude oil produc-
0.15% sulfur by weight (NRC, 1989, 2006). Sulfur is
tion, can be toxic to livestock. The toxic effects of these
incorporated into many essential molecules, including
gaseous forms of sulfur are better summarized separately
biotin, chondroitin sulfate, cartilage mucopolysaccharides,
from the dietary toxicoses.
coenzyme A, fibrinogen, glutathione, heparin, lipoic acid,
Plants can accumulate high sulfur concentrations.
mucins, and thiamine (NRC, 1989, 1998, 2006). In addi-
High sulfate water can cause a dual increase in total daily
tion to these biologically active compounds, sulfur is an
sulfur intake by way of the water and ingested proximal
intricate component of sulfur-containing amino acids,
vegetation. Plant sulfur concentrations have been shown
such as methionine, cysteine, cystine, homocysteine, and
to increase with increasing sulfate in the soil (Reddy
taurine. With the exception of thiamine and biotin, all
et al., 1981; Hardt et al., 1991; Leustek and Saito, 1999).
sulfur-containing compounds in the body can be synthe-
In soil matrices, sulfate can be actively reduced and pre-
sized from methionine (NRC, 1996). Thus, thiamine, bio-
cipitated; however, this only sequesters the sulfur until
tin, and methionine are essential nutrients in the diet of
environmental change allows the reoxidation of sulfur
monogastric animals, but ruminant microbes can synthe-
back to sulfate. During drought conditions, precipitated
size these compounds from inorganic sulfate in the diet
sulfur in the subsurface soil is exposed to greater oxygen
(Block et al., 1951). Species differences are such that cats
and potentially reoxidized. The resultant sulfate is then
cannot synthesize taurine from methionine, making it an
bioavailable for plant uptake during subsequent periods of
essential nutrient in their diets. Recommended daily die-
normal or high precipitation.
tary intakes of sulfur are 0.15%, 0.14% 0.26%, 0.15%
0.2%, and 0.2% 0.25% of the diet for horses, sheep, beef
cattle, and dairy cattle, respectively (NRC, 1985, 1988, BACKGROUND
1989, 1996).
Ruminants tend to be more sensitive to the toxic Sulfur is a nonmetal within group VIA of the periodic table.
effects of dietary sulfur/sulfate due to efficient microbial This group is sometimes referred to as the chalcogenides or
conversion to bioactive sulfur species in the rumen. But ore-formers, since many metal ores are sulfide or sulfate
both dietary and water sources of sulfur/sulfate have simi- salts. Sulfur has an atomic number of 16, an atomic weight
lar toxic potential and must be factored into the total daily of 32.07, and has four different naturally occurring atomic
intake in order to establish potential risk. Dietary feed masses from 32 to 36 (Rosman and Taylor, 1998). It can
sources that can contain high sulfur concentrations, which occur in four different oxidation states: 22 (sulfide), 0 (ele-
are frequently overlooked, include distiller’s byproducts, mental sulfur), 14 (sulfite), and 16 (sulfate). All valence
wet and dry distiller’s grains and gluten feeds. These pro- states, except elemental sulfur, are found in biologic mole-
ducts can also have significant batch-to-batch variability cules. Sulfur is utilized in the production of sulfuric acid,
in sulfur content, even from the same production plant. fertilizers, pigments, dyes, drugs, explosives, rubber, insec-
Due to their relative inexpensive nature, compared to ticides and detergents, as well as many inorganic salts and
grains, these potentially high sulfur materials are more esters. Although uniformly found in nature, industrialized
and more frequently being added to ruminant diets. countries are the largest users of sulfur materials.

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