Download sulfur in feed and water for beef cattle

SULFUR IN FEED AND WATER
FOR BEEF CATTLE
Chelsea Gordon, Ruminant Nutritionist
Shur-Gain, Nutreco Canada Inc.
SULFUR IN FEED AND WATER FOR BEEF CATTLE
Chelsea Gordon, Ruminant Nutritionist
Shur-Gain, Nutreco Canada Inc.
Recent ethanol industry expansion has resulted in a large increase in the amount of corn milling byproducts
available for animal feed. Approximately 85% of the distillers grains produced by ethanol plants are used by the
beef and dairy industry. This feedstuff has many desirable characteristics, such as high energy, protein, and fiber.
However due to the use of sulfuric acid to maintain fermenter pH levels, distillers grains also contains an
appreciable amount of sulfur (S). The S content of distillers grains can be extremely high and is also quite variable.
If not managed properly, high S concentrations in the diet, coupled with S from drinking water, may negatively
affect both animal performance and animal health.
Role of sulfur and it’s concentrations in feed and water.
Sulfur (S) serves many purposes in the ruminant animal. It is a component of amino acids methionine and
cystine, as well as B-vitamins biotin and thiamine and a number of other organic compounds. For most ruminants,
dietary S must be between 0.18 and 0.24% of DM to allow rumen microbes to produce sufficient S-containing
compounds to support microbial growth and to provide S-containing compounds for the host animal (NRC, 2005).
Sulfur consumed by cattle originates almost exclusively from two sources — feed and water. Both sources can
be highly variable and need to be taken into account when formulating rations. The S concentration of feedstuffs
commonly used in beef cattle rations are listed in Table 1.
Table 1. Sulfur concentrations (% of DM) of corn milling byproducts and common feedstuffs for beef cattle. 1
Feedstuff
corn
corn silage
alfalfa hay
dried distillers grain w/solubles
wet distillers grain w/solubles
condensed corn distillers solubles
wet corn gluten feed
corn gluten meal
steep
1
Sulfur practical range
0.11 - 0.17
0.10 - 0.20
0.21 - 0.54
0.40 - 1.30
0.40 - 1.30
0.80 - 1.50
0.40 - 0.90
0.80 - 1.20
0.80 - 1.10
Grant I. Crawford, University of Minnesota
Recent guidelines (NRC, 2005) provided two recommendations for maximum S levels based on the forage
concentration in the diet. For beef cattle diets containing less than 15% forage, the maximum tolerable
concentration is 0.30% S, and for diets containing greater than 40% forage the maximum tolerable concentration is
0.50% S. It is also noted that drinking water for cattle fed high-concentrate diets should not contain more than 600
ppm sulfate.
If sulfur content is analyzed in both water and most at risk feedstuffs, it’s easy to estimate daily sulfur
consumption using the Colorado State University sulfur calculator
(www.dlab.colostate.edu/webdocs/special_cases/sulfurcalc.cfm). The calculator estimates sulfur intake at 3
different environmental temperatures - assuming water intake increases during the summer months.
Below is an example of typical finishing diet with average inclusion level for distillers (% of feed given on DM
basis) (picture 1). Sulfate level in the water was assumed to be 500 ppm. In the case of a 22% distillers (DM) diet,
0.32% sulfur is provided by the diet which is above tolerable level for this type of diet (NRC 2005), and up to
0.12% will come from the water giving 0.44% total S consumption (picture 2).
A high distillers diet (30% DM) will provide a total of 0.46-0.52 % S with the same water analysis.
Some water sources might contain up to 5000 ppm sulfate. In this case S consumption will range 0.6-1.3% from
water alone.
Picture 1. Sulfur calculator input form.
Picture 2. Sulfur intake estimation.
Sulfur toxicity.
Mild cases of S toxicity may result in decreased average daily gain and feed efficiency, and may not be
recognized until the cattle have left the feedlot and closeouts are completed. More severe cases of sulfur toxicity
may result in polioencephalomalacia (PEM), which may also be known as brainers or polio. This condition is
caused when excess S in the diet is consumed and converted to hydrogen sulfide in the rumen. The excess
hydrogen sulfide can inhibit cellular respiration, which limits the amount of oxygen and energy delivered to the
brain and causes lesions and softening of the brain. Symptoms of PEM include separation from the herd, head
pressing, “star gazing” in which cattle stand with their head held back and upward, teeth grinding, and a staggered
gait. More extreme and advanced symptoms may include seizures, blindness, and coma, and may eventually lead
to death if not treated promptly.
Treatment of sulfur toxicity.
Although thiamine’s role in the occurrence of PEM is not entirely clear, it is the primary method of treatment for
afflicted animals. Addition of certain minerals, such as copper and zinc may assist in reducing the amount of S that
is converted to hydrogen sulfide in the rumen. Sulfur forms a complex with these minerals that reduces their
availability for absorption and utilization by the animal, and therefore supplementation of these minerals beyond
traditional recommendations may be needed as well as non-organic form might be partially replaced with organic
minerals. In addition to these treatments, high S-containing feedstuffs should be removed or limited in the ration.
Addition of roughage to the ration may also be helpful. If possible, high-sulfate water should be replaced or diluted
with lower-sulfate water.
Conclusions.
When formulating rations, the S content of feedstuffs and water needs to be taken into account. To manage the
variability in S concentrations associated with corn by-products, a safety margin should be included in the ration
formulation. This allows for a margin of protection if the S content of a load of distillers grains exceeds the usual
reported level by the ethanol plant. In hot summer months, distillers grains inclusion may need to be reduced,
especially in areas with high sulfate water due to increased S intake via elevated water consumption. In addition,
traditional management practices such as proper feed mixing and good bunk management should be emphasized to
ensure that distillers grains are uniformly mixed and delivered to cattle.
Unfortunately, the high S content of distillers grains is something we will have to deal with for the foreseeable
future, and may, at times, limit its inclusion in feedlot diets. Through water and feed sampling, careful ration
formulation, and proper management practices feedlot producers should be able to take advantage of this valuable
feedstuff.