Additional Information on Zearalenone

By Kimberly S. Graetz

In the industry-wide meeting at Keeneland on Thursday, May 10, zearalenone, a kind of mycotoxin, was put forth as a possible cause of the recent rash of late-term stillbirths, critical foals, and early fetal loss. But while experts seem to be in agreement it is a good possibility that zearalenone in particular is indicated, they aren't ruling out other possible causes or saying only that one mycotoxin is the sole instigator of illness. Whatever the cause, the effects are cumulative.

Fusarium species of molds are extremely common in growing plants and stored feeds, according to pasture and nutrition experts. Zearalenone is produced by Fusarium graminearum. According to the Merck Veterinary Manual, Zearalenone is a potent non-steroidal estrogen, and it is the only known mycotoxin with effects that are primarily estrogenic. "Zearalenone-contaminated grains and fodders can produce reproductive disorders when animals consume them. In cattle, dietary concentrations of greater than 10 parts per million may cause reproductive dysfunction."

The Merck Veterinary Manual also listed signs in other species, including: In multiparous sows (have produced more than one litter), the effects of zearalenone include diminished fertility, anestrus, reduced litter size, smaller offspring, and probably fetal resorption. Dairy heifers (cows which have never had a calf) can show signs including weight loss, vaginal discharge, nymphomania, and uterine hypertrophy. In pregnant heifers abortion can occur one to three months after conception, usually followed by multiple returns to service. Young male cattle can become infertile, with atrophy of the testes.

The Merck Veterinary Manual also states that, "Unless stock are severely or chronically affected, recovery of reproductive functions and regression of signs are usual one to four weeks after the intake of zearalenone stops."