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Cobb: Livestock producers should be cognizant of potential for botulism toxins in stored hay

by Wyoming Livestock Roundup

Livestock and horse owners should use caution when purchasing hay from unknown sources. Hay that has been improperly baled, contains dead animals or trash or that has been stored in wet conditions can be a thriving source for botulism. 

Botulism is a serious illness that is typically fatal. It is caused by a bacteria that dates all the way back to the Roman Empire – Clostridium botulinum

“This group of bacteria produces some of the most devastating diseases known, as the effects of their toxins have very rapid and frequently fatal results. As a group, these bacteria can be common in many soils and are frequently associated with poor sanitation or contamination of food sources,” according to Donald Cobb, a Casper veterinarian who has dealt with botulism cases.

Inside Botulism

Botulism is an anaerobe, meaning it grows in environments lacking oxygen. 

“Any type of feed where there is a lack of oxygen can have botulism growing in it,” Cobb explains. “Any time we have feed like a tight hay bale or a pile of grain where there is no air circulation, there is a chance for this organism to grow. 

“The organism itself, while it grows, does not produce problems. However, it emits an incredibly potent toxin that does,” he says.

Cobb recalls a producer who shot a fox on top of a hay bale and left the fox there to deteriorate. As the decomposition ran down through the hay, the bale became contaminated with botulism. The rancher fed the bale, and seven horses died as a result. 

In another well-documented case that occurred several years ago, a tremendous corn crop was harvested in the Midwest, and some corn was stored on the ground. Over 150,000 migratory fowl were lost to botulism after consuming the corn. 

Cobb explains that when feed sits on the ground and becomes wet and moldy on the bottom, botulism can occur.

Cobb shared another instance when a client had a down mule and a missing saddle horse. Both animals died. Cobb suspected botulism, and when he and his client tore open the bale of hay, they found a dead deer baled up amongst the forage. 

Avoiding garbage

“Why anyone would knowingly put garbage, dead animals or anything other than clean hay in a bale and cover it up is difficult to understand,” he says. “Big square balers can pick up anything, and some producers will pick up trash and throw it into the baler to hide it.” 

Unfortunately, if these bales become contaminated with botulism, the person feeding the bale won’t notice a lot of outward signs in his livestock. The first symptoms may be a bunch of dead animals. 

Susceptibility can be pretty uniform in any animal, Cobb says. 


If a producer doesn’t find the animal dead, the main symptom of botulism is a flaccid paralysis. 

“The animal will be fairly bright, alert, down and have either lateral or sternal recumbency. They will be totally unable to mount a muscular response,” Cobb explains. 

“What kills them is when it paralyzes the muscles of respiration,” Cobb continues. “Botulism destroys the nerve transmission to the muscles. The animal will be totally incapable of responding to any stimulus, and they have no control of their muscles.”

“Depending upon the dosage, death can occur in a relatively short period of time. They can go from normal, to staggering, to death within a few hours,” he states.


Although the condition can be treated with the right antitoxin, botulism has multiple strains, so the right strain would have to be identified for the treatment to be successful. In most instances, isolating the organism and determining what strain it is is a postmortem diagnosis. 

However, in Kentucky, where botulism occurs more frequently, some strains have been isolated, and some animals are given vaccines to prevent botulism. 

Being proactive

Cobb says no test exists to test bales of hay or feed for botulism. However, botulism has a putrid smell similar to the seven-way Clostridial vaccine.

“There is no such thing as good, poor quality feed,” he continues. “It only takes a small amount of botulism to kill an animal. Even if the contamination is removed from the bale, the bale is a total loss. The toxin can permeate through the bale.”

If bales are contaminated with botulism, Cobb recommends burning the hay. 

“If the hay is hot enough to burn, it should kill the toxin. It shouldn’t be able to survive that much heat,” he adds. 

If the toxin is in one bale of hay, chances are good that it could be in more than one. 

“Most producers take a lot of pride in what they produce,” Cobb says. “I would recommend sticking with good, reputable hay producers who are concerned with what they produce and have repeat customers year after year. If do that, we have done about everything we can to prevent the problem.”


Cobb suggests producers can also help prevent botulism by stacking hay to allow air circulation under the bottom bales, which can stop mold and other issues. 

He also suggests investing in a covered hay shed to prevent moisture from seeping into the top of the bales and traveling through them to the bottom bales. It also keeps the bottom bales dry. 

On a final note, Cobb says producers need to use common sense to protect themselves because no one else will do it for them. 

“We will be in a hay shortage for some time, and we may be forced to feed some feed we don’t want to,” Cobb notes. “If a rancher thinks that feed may be bad, don’t take a chance on it.”

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to

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