Horse Racing: Cherry tree cyanide linked to Kentucky foal deaths

Cyanide occurring naturally in black cherry trees is being blamed for more than 500 foal and fetus deaths in Kentucky.

But while scientists believe they have identified cyanide as the toxin affecting horses and the cherry trees as the source, part of the mystery remains.

Professor Thomas Tobin, of the University of Kentucky Gluck Equine Research Centre says it is unclear how it gets into the mares' systems.

The theory also implicates the Eastern tent caterpillar, which feed on the trees' leaves and are present in abnormally high numbers this spring.

Dr Jimmy Henning, a University of Kentucky agronomy professor, added: "There is an extremely close association between the presence of the cherry trees, the presence of the Eastern tent caterpillars and both early fetal losses and late-term abortions.

"We have to conclude the wild cherry-caterpillar complex is the lead suspect in the Mare Reproductive Loss Syndrome."

Dr Henning said tests have failed to support other hypotheses as to the cause of the outbreak, which began in late April.

Professor Tobin said the caterpillars are immune to cyanide from the black cherry tree, and one theory is that the mares could have ingested the caterpillars' faecal matter, which contained the cyanide.

For the past three weeks, scientists have been trying to determine why foals are being born sick or dying and why mares are aborting early-term pregnancies on farms throughout central Kentucky.

Only 24 deaths have been reported since Sunday and only four in the past two days. More than 500 deaths were reported between April 28 and May 19.