Cherries linked to foal deaths. (Clippings).

Equine researchers at the University of Kentucky suspect that wild black cherry trees (Prunus serotina) played a role in the deaths of hundreds of Kentucky foals this spring.

The cherry's leaves contain cyanogenic compounds and, when wilted, are known to be toxic to cattle and sheep, the university says. Wilted cherry leaves also attract eastern tent caterpillars, which were especially abundant in central Kentucky this spring.

Researchers at the university's equine research center suspect that grazing mares ingested the caterpillars' excrement, which would have been high in cyanide. That, in turn, caused the poisoning of the mares' fetuses.

In July, the researchers said their preliminary analysis of a survey of 150 horse farms confirmed those earlier theories. The analysis showed that the incidence of fatality was higher in cases where cherry trees or cherry seedlings were in or around the pastures and where caterpillars were abundant.

So far, the researchers have not recommended the wholesale chopping of wild cherries around horse farms. After all, the trees are valuable sources of timber and wildlife habitat and are thought to pose a potential danger to horses only in the spring when caterpillars are present. But the university has recommended against confining horses to small areas surrounded by wild cherry trees and called for the use of temporary fencing to close off areas next to lots of wild cherries to "provide an extra level of safety."