Source: University of Minnesota
Recognize the reported S content of distillers grains and the potential variability with it
Account for both diet and water S content when managing S intakes
S intake shouldn’t go over 0.30 percent diet DM in feedlot cattle
High S intake can reduce average daily gain and feed efficiency and can lead to PEM
Supplementing diets with certain minerals or antimicrobials can help prevent or reduce PEM events
Sulfur (S) plays a key role in ruminant animal nutrition. While most forms of S are relatively nontoxic, hydrogen sulfide is highly toxic to cattle. Hydrogen sulfide is the compound that causes the rotten egg smell related to S.
Most ruminants need 0.18 to 0.24 percent dry matter of dietary S.
The beef cattle industry commonly feeds distillers grains, which contain sulfur. The S content of distillers grains can be really high and vary. You must properly manage S in the diet. Too much S in the diet, including drinking water, may harm cattle performance and health.
Sulfur sources and amounts
Cattle get most of their sulfur from feed and water, which can vary in amount. You must consider both sources when formulating rations.
Table 1 shows the S content of common feedstuff for beef cattle rations according to the 1996 Beef National Research Council (NRC).
Table 1. Sulfur content of corn milling byproducts and common feedstuffs.
S content varies in milling byproducts
Changes in S content of milling byproducts is more concerning than high S amounts. Changes can occur within and among ethanol plants.
Eight Minnesota ethanol plants ranged in S content from 0.34 to 1.05 percent and averaged 0.69 percent for dried distillers grains (DDGS).
The amount of WDGS you feed and the temperature affect the total intake of S (see table 2).
Table 2. Effect of temperature and WDGS S content on total S intake by a 1,000-lb feedlot steer1,2.
Water sulfate content
You must account for water sulfate content when considering total S intake of cattle. Very high water S may limit the use of corn milling byproducts in rations.
Water is generally below 200 parts per million sulfate in the main cattle feeding areas of Minnesota. But, water sulfate content can greatly vary and be site-specific. You should test water sulfate content in any area you feed cattle.
Make sure to account for any changes in water intake. A 1,000-pound steer will drink about 9 gallons of water daily when the temperature is 40 F and nearly 21 gallons when the temperature is 90 F. Higher water intake means higher S intake. Thus you may need to feed less distillers grains during the hot summer months if you have high-sulfate water.
Sulfate is 0.35 percent S, thus a 30 part per million water sulfate content would equal about 10.5 parts per million of S. Water sulfate content less than 1,000 parts per million is usually safe (Table 3).
Table 3. Maximum recommended water sulfate content for cattle1.
Effects of high sulfur on cattle
According to the 2005 NRC, the maximum tolerable S content in beef cattle diets are as follows:
0.30 percent S for diets with less than 15 percent forage
0.50 percent S for diets with more than 40 percent forage
The 2005 NRC recommends less than 600 parts per million sulfate in drinking water for cattle fed high-concentrate diets.
Reduced mineral use
High S may affect cattle health and performance by decreasing the use of minerals by the animal including
Suttle 1991 saw a 50 percent decrease in copper use when diet S content increased from 0.2 to 0.4 percent.
Wright and Patterson 2005 found that copper declined 58.5 percent in steer livers when water sulfate increased from 404 to 3,947 parts per million. A second experiment showed copper declined 88.6 percent in steer livers when water sulfate content increased from 441 to 4,654 parts per million. For the first and second experiments, total S intake was 0.93 and 1.1 percent of DM for the high S treatments, respectively. The control treatments each contained about 0.26 percent total S.
As S content increases in beef cattle diets, average daily gain (ADG) and feed efficiency declines.
Spears and Lloyd 2005 found diets with 0.31 and 0.46 percent S reduced steer DM intake compared to diets with 0.13 percent S. Steers had lower ADG with a 0.41 percent S diet than with a 0.13 percent S diet.
More extreme effects of excess S may lead to the central nervous system disorder polioencephalomalacia (PEM), also known as polio or brainers. PEM is a softening of the gray matter of the brain. The symptoms of this disorder may initially include:
Separation from group
Going off feed
“Stargazing,” in which cattle hold their head in a high, upward-looking position
A staggered gait
More advanced symptoms may include:
PEM shares symptoms with other common gut or respiratory disorders and often gets misdiagnosed.
Types of PEM
Thiaminase-induced PEM happens when thiaminase I production occurs in the rumen. Thiaminase breaks down the B vitamin thiamine.
Researchers found that containing bracken fern and amprolium relate to decreased thiamine use.
Ward and Patterson 2004 didn’t see a significant decrease in PEM after giving steers 1 gram per head per day of thiamine when water had 3,786 parts per million of sulfate. But PEM incidence dropped from 14.3 percent without supplement to 4.8 percent with supplement thiamine.
Sulfur-induced PEM has symptoms and outcomes similar to those of thiaminase-induced PEM. S-induced PEM is directly due to S content. Water and feed sources of S have been implicated in cases of S-induced PEM. Patterson and Johnson 2003 reported the following PEM events in steers with the respective total S intakes.
0 percent incidence with 0.27 percent of DM
15 percent incidence with 0.74 percent of DM
12.5 percent incidence with 0.93 percent of DM
McAllister et al. 1997 reported that PEM events in feedlots are seasonal and relate to days on feed. The incidence of PEM peaks in the summer likely due to increased water S intake.
PEM incidence also peaks between 15 and 30 days on feed possibly from adapting cattle to a high-concentrate diet. Sager et al. 1990 and Low et al. 1996 saw clinical signs of PEM beginning on day 15 after adapting cattle to a high-concentrate diet with excess S.
Dougherty and Cook 1962 reported that ruminants normally inhale eructated (belched) gases, including hydrogen sulfide, into their lungs. Cattle can inhale as much as 60 percent of the gas they eructate. Hydrogen sulfide absorbs across the lungs during eructation, which can cause PEM.
Prior to eructation, gases build in the upper rumen. Acidic conditions allow for more gas to build up, which makes cattle fed high-concentrate diets prone to toxicity from excess S intake. There’s more hydrogen sulfide in the built-up gas than in ruminal fluid.
Hydrogen sulfide content in built-up gas peaks about 1 to 3 weeks after starting a high-S diet. Increases in hydrogen sulfide content relates to clinical PEM symptoms.
Treating sulfur toxicity
Intravenous thiamine is the main treatment method for animals with sulfur toxicity. Cebra and Cebra suggest giving 10 milligrams per kilogram of bodyweight of thiamine. You should continue to give this dose every 6 hours for a few days. After the first dose, you can give the injections directly into the muscles. You can give the first injection in the muscle if the animal has milder symptoms. You may need to give multiple injections if the cattle don’t respond to a single injection.
Remove or limit high S-containing feedstuffs from the diet as soon as PEM occurs. Adding roughage to the ration may help. Replace or dilute high-sulfate water with lower-sulfate water if possible.
Blindness may remain long after other signs have gone away in severely affected animals.
Managing high sulfur feedstuffs and water
Here are few ways to manage high sulfur content.
Limit the amount of high S feedstuffs or water consumed
Offer feed additives that may offset high S intakes
Use reported measures of S variability in feedstuffs to maximize use of high S feedstuffs without causing problems
The best way to manage S content is by using additives and accounting for feedstuff variability.
Monitor diet thiamine content to make sure cattle are receiving enough. You may want to consider supplemental thiamine to avoid thiaminase-induced PEM. Gooneratne et al. 1989 suggests supplemental copper for cattle with high S intakes. Supplementing copper up to 50 parts per million of diet DM will reduce copper and thiamine deficiencies.
When conditions may favor PEM, providing oxytetracycline or chlortetracycline may help reduce PEM events. These two antimicrobial additives will reduce microbial activity in the rumen and thus reduce the amount of S that gets changed to hydrogen sulfide.
Feedlot producers should include a safety margin in ration formulation to manage S content variability in distillers grains. This allows for some protection if the S content of a load of distillers grains exceeds what the ethanol plant reported.
Other management tips
Make sure to mix feed properly and distribute it evenly throughout the bunk.
Even if an analysis of distillers grains S content is available from ethanol plants, producers should sample each load of distillers grains as it arrives. The turnover time for sample analysis is usually longer than the useful life of the distillers grains. Pritchard 2007 recommends freezing samples until that load of feed is gone. You’ll then have a sample for analysis if problems arise while feeding this load of distillers grains.
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