Following is from the University of Kentucky’s College of Agriculture as of Friday, May 25, at 5 p.m. More information can be found on their web site at

We are able to report significant recent progress in accounting for Mare Reproductive Loss Syndrome (MRLS). Observations to date implicate cyanide or cyanogenic compounds as the causal agent. Wild black cherry trees are the likely source of these toxins. Limited recent imply the Eastern Tent Caterpillars may be directly or indirectly involved in the delivery of cyanogenic compounds to horses.

We want to emphasize that the current observations are preliminary, must be confirmed, and that further validation is absolutely essential. We have not yet met reasonable standards of scientific proof. Information summary briefs from several of the presentations made at the Mare Reproductive Loss Syndrome Information Sharing Meeting held yesterday at the Keeneland Sales Pavilion are posted to our web-site. In addition, several audio files of sound clips from the speakers are also posted. A replay of the entire meeting is also provided by a link with

There are several suggested recommendations from UK Extension Specialists for Pastures and Forages, Dr. Jimmy Henning and Dr. Garry Lacefield for horse producers as follows:

1. It should be considered safe to turn horses back out to pasture.

2. Mow pastures to dislodge any larvae or caterpillar
excrement from the leaves.

3. Do not confine horses in small areas that are surrounded by wild cherry trees.

4. Using temporary fencing to skirt off fence line areas next to high numbers of wild cherry trees may provide an extra level of safety.

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