Moldy corn poisoning is not a household term, even among veterinarians. The devastating condition to horses, however, is something that every horse owner needs to be aware of.
There are several frustrating things about moldy corn poisoning. It is almost impossible to detect in affected feed, there are no known preventive measures other than not feeding corn, there is no cure, and the animal has to be dead in order to confirm the diagnosis.
The last time there was a serious outbreak of moldy corn poisoning, conditions were just like they are this year: There was a summertime drought, a wet fall, and wildly varying temperatures during the fall and early winter. These conditions foster growth of an invisible toxin in corn which causes poisoning in livestock. Horses are especially at risk.
Given this year's conditions, Dr. Lee Miller, a veterinarian who practices in Howard County, feels that the horse communityshould be informed. Miller notes that during the 1986 outbreak of moldy corn poisoning, Maryland horsemen were not informed of the problems until a dozen or more horses had died.
"By the time the animal shows symptoms it is too late," says Miller. "Death will usually occur after three weeks or more of feeding the contaminated corn. It appears as though a fair amount of corn has to be fed in order for a problem to occur. The effect seems to be cumulative in the horse's system, and horses may die even after they stop eating corn.
"Before dying the horse will exhibit a change in personality, signs of blindness, loss of appetite, muscle spasms, and aggression. Death usually follows within 24 hours."
Miller says that a diagnosis is easy to makeduring a necropsy. The horse's skull and brain are cut down the middle and the central area of the brain appears to have "turned to mush,it will look soft and milky," he said.
Veterinary history may have been made recently at the University of Pennsylvania's New Bolton Center for Veterinary Medicine. After being shown an article on moldy corn poisoning in the January Maryland Farmer, a veterinarian diagnosed a possible case of moldy corn poisoning at a farm where four horses had already died of undiagnosed illness.
Specimens from one of the horses who previously died at the farm in Reading, Pa., were takento New Bolton, and it was determined that the cause of death was moldy corn poisoning.
The ill horse (the fifth at this farm to be affected) was treated aggressively with DMSO, saline solution and Lasix to relieve pressure on the brain. The prognosis is that the horse will survive.
Miller says that several molds are easy to detect in corn, with the naked eye or with ultraviolet light. Mold in itself is not necessarily toxic, so the presence of mold alone does not mean that fatal toxins are present.
The highest risk is run by those who have a corn crib and use ears of corn to supplement their horses' feed, Miller says.
"The problem is usually pretty localized," Miller says. "Several feed operations have stopped using corn in their mixtures, and that puts you in a quandary, because you can't beat corn for energy in the horse's nutrition."
Miller's wife, Marilyn, is a competitive trail rider and depends on corn for her horses' energy needsduring 100-mile competitions.
"I checked where we get our feed, and this last batch was made with corn harvested last year so it should be all right. But the next batch will be made with corn that I don't want to take a chance on, so it will be back to feeding barley," she said.
Dr. Lee Miller suggests the following as an alternative horse feed mixture that contains no corn:
* 80 pounds of crimped barley or oats, or any combination
* 10 pounds of pelleted feed, 38 percent protein
* 1 pound trace mineral salt
* 1 pound DiCal phosphate
(8 pounds of molasses can be added to this mixture if desired)