Although it doesn't happen frequently, spoilage of silage, hay, and grain can sometimes pose a serious threat to livestock. Producers and farm managers can minimize the threat by becoming aware of the different toxins that can harm cattle, horses and other animals.

"Mycotoxins, botulism, and listeriosis are very real threats that livestock producers should become knowledgeable about," said Mike Collins, forage physiologist in the University of Kentucky College of Agriculture. "These toxins can cause anything from weakness and poor appetite in livestock all the way up to paralysis and even death."

Mycotoxin is the name for a variety of toxins produced from molds. They primarily affect grains but also can contaminate forages. Mycotoxin-related health problems in horses and other animals include reduced appetite, vomiting, intestinal problems, neurological problems and reproductive problems.

"One of the categories of mycotoxins we see in this region of the country affects stored grains and silages, and also hay," said Kate Jacques, director of nutrition for Alltech, a Kentucky-based company specializing in animal nutrition products. "This general category would include fusarium toxins and aflatoxins."

Mold and accompanying mycotoxins can occur occasionally in hay when moisture is 20 percent or above. Jacques said mold inhibitors have proven effective in combating mycotoxin contamination.

"Better education is certainly a key factor in preventing losses, so we recommend talking to qualified people such as university faculty and Extension specialists, and also taking advantage of educational opportunities," said Peter Karnezos, Alltech's vice president for domestic sales. He said meetings, such as the one his company plans for early November on mycotoxins, are a good way to stay informed.

Consumers generally associate botulism with spoiled human foods, but the clostridium bacterium that causes illness also can occur in livestock feeds.

"Botulism in hay is usually associated with dead animals such as snakes or rabbits that are killed during the harvest process and get baled, and when this occurs the affected bale should not be fed," Collins said. "The more common form of botulism is when spoiled silage is fed to animals."

Anytime silage spoils instead of properly fermenting there is an opportunity for botulism bacteria to form. To prevent this formation, silage should be produced at a moisture level of 70 percent or below. Allowing the crop to wilt a little before harvest decreases moisture content and helps ensure adequate ensiling.

Listeriosis, also called circling disease because of its effect on sheep and cattle, is associated with soil contamination of the crop during harvesting or storage.

"For instance we have seen it occur when round bales were pushed along the ground while making round bale silage and some soil gets incorporated into the bale," said Collins. "Listeriosis, similar to botulism, is also associated with poor fermentation such as a silo improperly covered or round bale silage with a hole in it or an inadequate amount of stretched film around it."

With both listeriosis and botulism, an offensive odor will typically signal a problem to the producer.

"When that happens and you see a lot of spores and dust there is also a chance of heat damage to the hay because moisture generates heat and that ties up protein that otherwise could have been available to the animal," said Collins.

Collins said the main thing to remember is that preventing botulism, listeriosis, and mycotoxins depends on proper fermentation in the case of silage, proper moisture content in the case of hay, and proper drying in the case of grain. He cautioned that hay, silage, or grain that has an offensive odor should be discarded and not fed to livestock.