Sulfur is essential for all animals because S-containing compounds,
such as amino acids, hormones, B-vitamins, and co-enzymes,
are required for normal metabolic, structural, and
regulatory functions of all living organisms (Goodrich and
Garrett, 1986). The sulfur concentration for the diets of beef cattle
recommends by the National Research Council is 0.15% (w/w, on
dry matter basis) of the diet, while the maximum tolerable level
of dietary sulfur has been based only on the percentage of theforage in the diet. Most of the dietary sulfur ingested by ruminant
animals is converted to sulfide by rumen microbes, primarily
rumen bacteria, with S-containing amino acids being fermented
to sulfide while sulfate being reduced to sulfide by ruminal sulfate-reducing
bacteria (SRB) (Coleman, 1960). Although being a
small guild of bacteria in the rumen, SRB can have significant
impact in cattle fed diets with high sulfur content, such as dried
distiller grain with soluble (DDGS).
In the last few years, DDGS has become abundantly available
and cost competitive as a feed ingredient because of the expansion
of bioethanol industry in the United States and beyond. In 2013,
the US had nearly 200 bioethanol plants in operation that churned
out an estimated nearly 35 million tonnes of distillers grain
(mostly corn-based). Corn-based DDGS contains, on average, 30%
crude protein (CP), of which 55% is ruminally undegradable, and
Sulfur is essential for all animals because S-containing compounds,such as amino acids, hormones, B-vitamins, and co-enzymes,are required for normal metabolic, structural, andregulatory functions of all living organisms (Goodrich andGarrett, 1986). The sulfur concentration for the diets of beef cattlerecommends by the National Research Council is 0.15% (w/w, ondry matter basis) of the diet, while the maximum tolerable levelof dietary sulfur has been based only on the percentage of theforage in the diet. Most of the dietary sulfur ingested by ruminantanimals is converted to sulfide by rumen microbes, primarilyrumen bacteria, with S-containing amino acids being fermentedto sulfide while sulfate being reduced to sulfide by ruminal sulfate-reducingbacteria (SRB) (Coleman, 1960). Although being asmall guild of bacteria in the rumen, SRB can have significantimpact in cattle fed diets with high sulfur content, such as drieddistiller grain with soluble (DDGS).In the last few years, DDGS has become abundantly availableand cost competitive as a feed ingredient because of the expansionof bioethanol industry in the United States and beyond. In 2013,the US had nearly 200 bioethanol plants in operation that churnedout an estimated nearly 35 million tonnes of distillers grain(mostly corn-based). Corn-based DDGS contains, on average, 30%crude protein (CP), of which 55% is ruminally undegradable, and
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