Ergotism: Concerns for Livestock Fed Contaminated Feed Sources
Livestock producers feeding grains or screenings to cattle, sheep, horses and other species should be aware of the potential for ergot contamination in feed sources. Recognizing ergot is the first step to preventing toxicity resulting from consumption of significant amounts of ergot.
Ergot is a parasitic fungus (Claviceps purpurea) that grows in the seed heads of grasses and grains. When conditions are right and spores are present, large, black ergot bodies can develop in the grain’s seed ovary. The fungus is particularly prolific when cool, wet weather occurs during the pollination stage. It is highly prevalent in rye, but can also be present in wheat, barley, oats, brome, fescue, blue, timothy, western and intermediate wheatgrass and other grasses.
Ergotism, the condition resulting from consuming toxic amounts of ergot alkaloids, has been documented historically for centuries. It came to be known as ‘St. Anthony’s Fire,’ after a plague of ergotism killed thousands of Europeans in the 17th Century after rye was introduced as a grain crop. Ergot was also used medicinally in ancient times both in China and in the Middle East.
High levels of ergot alkaloids cause restriction of blood flow in the body, which results in gangrenous sores and tissue loss on extremities: tails, ears, lower legs and hoof walls of cattle are often affected. This also causes abortions in livestock due to restricted blood flow to the placenta. Other symptoms may include fever, staggering, convulsions, muscle spasms, altered endocrine function, decreased reproductive performance or milk production, abortions, and feed refusal. Livestock fed grain containing ergot alkaloids may simply not gain well or show signs of heat susceptibility during periods of warm weather.
Gerald Stokka, North Dakota State University Extension Veterinarian, said that with no universal standard for the safe concentration of ergot in feed, producers must exercise caution with potentially contaminated feed sources, especially grain screenings into feeding programs, and he recommends getting feed grains tested for an accurate assessment of ergot alkaloid content. Ergot testing is performed on the feed itself, not on biological tissues.
“The NDSU Veterinary Diagnostic Laboratory at Fargo analyzes grains and grasses for ergot alkaloids,” he said. “Because of the huge variation of different ergot alkaloid concentrations in individual sclerotia, the evaluation of sclerotia in grain by weight for toxicity is misleading. We recommend producers submit a representative sample of grains and grasses to a veterinary diagnostic lab for ergot alkaloid testing before feeding it to livestock. The analyses will provide information on the risk of ergot alkaloids to different species of animals.”
Dry conditions during the 2021 growing season were not conducive to ergot formation. Dr. Russ Daly, South Dakota State University Extension Veterinarian said that they refer any testing needed to NDSU, or on occasion to the University of Missouri.
“In South Dakota we are much more apt to run into ergot issues in animals grazing pasture grasses that are contaminated,” Dr. Daly said. “Cases are usually seen in years with cool, damp spring weather followed by a warm growing season. This results in infected and plentiful grass that is grazed and hayed after seed heads are produced. We also documented a contaminated feed source as the cause of ergotism in a group of bulls being fed several years ago. Producers and their veterinarians should check with their state’s testing labs to find our their capabilities.”
“When environmental conditions are conducive to the development of ergot, we see more samples of grains and feed come in for testing, especially when ergot it noticed in wheat crops or rye crops,” Dr. Stokka said. “We have had wheat screenings contaminated with ergot come in for testing. Or occasionally a producer will send in a feed sample to be checked after signs and symptoms in animals, such as lameness, necrosis of tail or ears were noticed in livestock.”
Scranton Equity Feeds, feed manager Brent Sanford said that he does not use screenings in the feed products they manufacture at the Scranton, North Dakota facility. He has a zero tolerance level for ergot in any feed wheat they purchase.
“The first question I ask is whether the wheat contains any vomitoxin or ergot,” he said. “If the answer is ‘a little’ we just don’t buy it. And when a load comes in we grab a sample before it’s unloaded and if I see any ergot we will not take it for feed. Our nutritionist advised that it is simply not worth the risk.”
Sanford said that the 2021 wheat crop in that area did not have much ergot troubles, but a couple of years ago when the weather was wetter, he saw a lot.
“Producers can get away with feeding ergot contaminated grain in small amounts if they are careful, but we don’t want to risk contaminating any feed products,” he said. “We used to use a lot of screenings in our feed products, but grain is coming in so much cleaner these days that the elevators don’t have a lot of screenings available. We just don’t want to take a chance on using a load and end up with someone having a problem.”
Sanford knew a local producer who lost around twenty head of cows to ergot poisoning a few years ago.
“He knew there was some ergot in the grain he was feeding but didn’t think there was very much until he had problems,” he said. “The only way to really know is to get it tested. You might look at your grain and think there’s not very much ergot in it, but after you actually check it a lot of times the density is higher than you think it will be from a glance.”
Different species of livestock will react differently to ergot alkaloids, and ergot can contain a variety of different toxins in varying amounts. If livestock suffer from ergotism, the only remedy is to remove the feed that contains the toxins.
“The amount of ergot alkaloids present varies widely,” Dr. Stokka said. “Ruminants consuming rations with 0.3% to 1% or more sclerotia can develop gangrenous ergotism. Researchers estimate that ergot alkaloid concentrations between 0.2 and 0.8 milligram per kilogram or part per million in the total feed ration can produce ergotism in livestock. Any amount of noticeable ergot in feed is a reason not to include in a feed ration.”
When it comes to ergot, prevention is the best cure.
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