May 25, 2001 | By: Mark Eclov

As the evidence continues to build, it is strongly believed that the hay fields and pastures of Kentucky are now clear of the agents that caused Mare Reproductive Loss Syndrome, but that first cuttings of hay should be carefully examined and handled with care.

Jimmy Henning, an agronomist in the UK College of Agriculture, gathered many of the pasture samples used in the research and has recently been assuring horse owners that it is now safe to once again graze horses on all pastures.

Henning also feels that hay producers can feel safe about selling second cuttings of hay as long as they follow their regular scouting procedures to insure the lack of other normal problems seen in a given year.

But Henning warns that first cuttings of hay might have to be discarded or a least not fed to horses if they noticed heavy populations of tent caterpillars in April and have fields located near cherry trees.

"The first cutting of hay seems to be the only thing implicated," said Henning. "It is going to be a farm by farm deal on carefully examining the first cutting of hay and the field's proximity to cherry trees."

If that combination of insects and trees was present, Henning says that even testing a large batch of hay bales might not be enough to identify a dangerously high level of caterpillar parts and excrement.

"It is a lot like checking for blister beetles in hay in that if you don't check for them in the field, you might not sample enough bales of hay to know that you have a significant problem." added Henning.

After submitting hundreds of pasture samples for testing from both affected and unaffected horse farms, the research findings methodically discounted a long list of possible pasture-related sources of Mare Reproductive Loss Syndrome.

White clovers, ergot-type alkaloids from bluegrass and orchard grass and tall fescue alkaloids have all been cleared as suspects. Henning noted that no Kentucky hay sample baled before May 6 had tested positive for Fursarium mycotoxins.

"It is therefore highly unlikely that properly cured hay from first or subsequent cuttings in Kentucky will cause any mycotoxin related problems in horses," said Henning.

But in his conclusions, discussed during the May 24 briefing held at the Keeneland Race Track, Henning noted that there was an extremely close association between the presence of wild cherry trees and high numbers of eastern tent caterpillars and that they had to be considered a leading suspect in the cause of Mare Reproductive Loss Syndrome.

While the research will continue to reinforce this theory of MRLS, Henning says it is time to clear Kentucky's pastures and hay fields of the stigma of continued contamination and to do a good job or checking out the first cutting of hay.