Managing sulfur in beef cattle feed and water

Sulfur (S) plays a key role in ruminant animal nutrition. While most forms of sulfur are relatively nontoxic, hydrogen sulfide is highly toxic to cattle. Hydrogen sulfide is the compound that causes the rotten egg smell related to sulfur.  

Most ruminants need 0.18 to 0.24 percent dry matter of dietary sulfur.

The beef cattle industry commonly feeds distillers’ grains, which contain sulfur. The sulfur content of distillers’ grains can be very high and vary widely. You must properly manage dietary sulfur. Too much sulfur in the diet, including in drinking water, may harm cattle performance and health.

Effects of high sulfur on cattle 

According to the 2005 NRC, the maximum tolerable sulfur content in beef cattle diets is 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 a sulfate level of less than 600 parts per million in drinking water for cattle fed high-concentrate diets.

Reduced mineral use

High sulfur may affect cattle health and performance by decreasing the use of minerals by the animal, including:

• Copper
• Iron
• Zinc
• Selenium

Researchers reported a 50 percent decrease in copper use when the diet S content increased from 0.2 to 0.4 percent. In a 2005 study, copper declined by 58.5% in steer livers when water sulfate increased from 404 to 3,947 parts per million. Copper declined 88.6 percent in steer livers when water sulfate content increased from 441 to 4,654 parts per million. In the first and second experiments, total S intake was 0.93% and 1.1% of DM for the high S treatments, respectively. The control treatments each contained about 0.26 percent total S.

Decreased performance

As sulfur content increases in beef cattle diets, average daily gain (ADG) and feed efficiency decline.

Diets containing 0.31 and 0.46 percent S reduced steer DM intake compared to a 0.13 percent S diet. Steers had lower ADG with a 0.41 percent S diet than with a 0.13 percent S diet.

Polio (PEM)

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 the group
• Going off feed
• “Stargazing,” in which cattle hold their head in a high, upward-looking position
• Head pressing
• Teeth grinding
• A staggered gait

More advanced symptoms may include:

• Blindness
• Seizure
• Coma

PEM shares symptoms with other common gut or respiratory disorders and often gets misdiagnosed.

Thiaminase-induced PEM

Thiaminase-induced PEM happens when thiaminase I production occurs in the rumen. Thiaminase breaks down the B vitamin thiamine. Researchers found that feed containing bracken fern and amprolium is associated with decreased thiamine requirements.

There was no significant decrease in PEM after giving steers 1 gram per head per day of thiamine when water contained 3,786 parts per million of sulfate. But PEM incidence dropped from 14.3 percent without thiamine supplementation to 4.8 percent with thiamine supplementation.

Sulfur-induced PEM

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. The following PEM events were observed 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

PEM events in feedlots are seasonal and are associated with days on feed. PEM peaks in the summer are likely due to increased sulfur intake in water.

PEM incidence also peaks between 15 and 30 days on feed, possibly due to adaptation to a high-concentrate diet. Researchers in the 1990s saw clinical signs of PEM beginning on day 15 after adapting cattle to a high-concentrate diet with excess S.

Belching

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.

Before eructation, gases build up in the upper rumen. Acidic conditions allow more gas to accumulate, making cattle fed high-concentrate diets more prone to sulfur toxicity. 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 relate to clinical PEM symptoms.

Treating sulfur toxicity

Intravenous thiamine is the primary treatment method for animals with sulfur toxicity. The suggested dose of thiamine is 10 milligrams per kilogram of body weight. 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 persist long after other signs have resolved in severely affected animals.