Lush clover growth in pastures can add to better livestock production. Clover grown in wet weather can also lead to "slobbers" in livestock, particularly horses, said specialists at the University of Missouri.
A fungus growing on clovers produces a toxin, slaframine, that can cause gastro-intestinal upsets in horses and cattle. The most noticeable symptom is excessive salivation.
"It's more of a nuisance, rather than a serious health threat," said Wayne Loch, MU horse specialist. "A horse can produce quarts of saliva, which in the most severe cases can lead to dehydration."
Tim Evans, a toxicologist at the MU School of Veterinary Medicine, said he receives more inquires regarding horses than cattle. "Although high doses of slaframine can cause more serious problems, most of the cases we hear about are limited to excessive salivation, which particularly concerns horse owners," he said.
The quick cure is to take animals off the infected legumes, which reduces symptoms in a couple of days. "If symptoms persist, it may be a dental problem or a foreign object, such as plant awns, in the mouth," Evans said.
Slobber symptoms are often associated with infected red clover, said Craig Roberts, MU forage specialist. However, the pathogen, a Rhizoctonia related to the fungus that causes brown patch in lawns, can be found on other clovers. Those include white and alsike clovers commonly found in Missouri pastures.
The toxin remains stable on hay cut, cured and baled. This most often occurs on second-cutting red clover hay, the specialists noted.
The offending hay may not appear moldy even though it contains the fungus, said Laura Sweets, MU plant pathologist with the Commercial Agriculture Program. On growing clover, the condition is known as "black patch disease." Leaf symptoms are lesions that range in color from brown to grayish-black. The spots usually have concentric rings.
Evans expects to start seeing cases in June after a wet spring.