All hay contains mold, but when the mold becomes noticeable decisions must be made about whether or not to feed it to livestock.
Noticeable mold, detected by sight and smell, usually makes hay less palatable, which can result in lower intake or animals refusing to eat the hay.
Other problems, including illness in animals, can occur from the toxic byproduct, mycotoxins, which mold fungi produce. Not all molds produce mycotoxins and the amount produced is unpredictable, making the decision to feed moldy hay burdensome. Mycotoxins are generally impossible to detect. Expensive lab tests can be conducted, but they are time consuming and
usually specific for only one type of mycotoxin.
Direct negative affects from moldy hay also are difficult to document because they affect livestock differently. Horses may be the most sensitive to mold among livestock. Mold spores often contribute to respiratory and digestive problems such as colic or heaves in horses. Cattle are less affected by mold, but certain molds can cause mycotic abortions or aspergillosis, a fungal infection. Humans also can be affected by mold spores. The spores cause a condition called farmer's lung where fungus grows in lung tissue. People need to avoid breathing in mold spores.
The best solution is to use common sense and minimize feeding moldy hay to more sensitive animals like horses or pregnant cows. This requires good observations. Look for respiratory difficulties and off-feed or feed refusal. Sometimes uncoordinated or odd movements can be a sign of sensitivity. Mixing moldy hay with other feedstuffs can sometimes dilute problems, but be careful that the animals are not sickened by tricking them into eating bad hay that they normally would refuse.
Dave Varner is an Extension Educator with the University of Nebraska Cooperative Extension office in Dodge County. Dave may be contacted at 727-2775, 1206 West 23rd Street in Fremont, or at dvarner1@unl.edu
