Dealing With MRLS on the Farm: No Magic Bullet

From the Dec. 22 issue of The Blood-Horse
Kentucky farm managers and owners are taking steps to prevent the reoccurrence of mare reproductive loss syndrome while fervently hoping last year's devastation was a one-shot deal. There are almost as many theories of what caused MRLS as there are people addressing the problem, so preventative measures differ from farm to farm.

Primary preventative measures, put out by the Gluck Equine Research Center at the University of Kentucky, included keeping pregnant mares away from wild cherry trees and the Eastern tent caterpillars that feed on such trees, frequently clipping pastures used by pregnant mares, and offering hay to horses in pasture. However, most farm managers believe the cause of MRLS cannot be pinpointed by science.

"In my opinion what caused this was a witch's brew of the perfect storm," said Steve Johnson, president of Margaux Farm near Midway, Ky. and the outgoing president of the Kentucky Thoroughbred Farm Managers' Club. "There was a whole myriad of criteria that culminated at one particular time. I'm not hearing a universal movement to do anything extreme because we don't really know that there's a specific direction to go in. Everybody has to look at their own situation and make the best management decision given his farm and his program."

Jim Squires, who owns Two Bucks Farm near Versailles, and who bred 2001 Kentucky Derby (gr. I) winner Monarchos, actually suffered losses from MRLS a year earlier than most farms. "I had a terrible time breeding mares in 2000 for the 2001 season. Out of 15 mares only five healthy foals were born.

"We had clover already coming up in February that was gnawed down to the ground, to dust. I always thought it was the clover. But even though I didn't buy into the tent caterpillar theory, I cut down my cherry trees anyway since they were a nuisance. I also have my own feed, and have put mycotoxin binders into it as opposed to adding it separately."

Arthur Hancock III, owner of Stone Farm near Paris,Ky., advanced the theory last spring that clover poisoning was behind MRLS. "Nitrogen causes cyanide poisoning. That's a scientific fact," he said. "When it doesn't rain, nitrogen content is high, and we didn't have rain all of April. It was the weirdest April I've ever seen."

Suzi Shoemaker owns and manages Lantern Hill Farm near Midway. She feels that MRLS had its roots in the climatic condition that saw warm weather followed by cold, and then warm again, leading to mycotoxins on the grass.

"It's good to reduce cherry tree numbers since they're toxic to all kinds of livestock, but I don't think they would have had this wide-ranging impact. I'm still thinking grass. Usually by Kentucky Derby Day you can throw hay in the field and mares won't touch it. But this year we threw it and they were still eating it, so we fed a lot of hay, and that's why I think we got off lightly. We lost six pregnancies out of 60 mares bred, and had no foals that were sick.

"Nobody really knows what caused MRLS. I think the scientists were pressured to come up with some magic bullet and they came up with cherry trees, but I don't believe it."

Eric Hamelback, who just assumed the presidency of the Farm Managers' Club, agrees that "ultimately nobody knows what created MRLS," and suggests farm managers and owners consult with their veterinarians before undertaking a plan of action. Hamelback, assistant farm manager of Adena Springs near Versailles, said they've removed the majority of the cherry trees on the farm. "Cherry trees were a factor--the fields and barns where we had our losses were lined with cherry trees--but you're looking at a multitude of factors."

As far as the upcoming boarding season, which has created concern for local operations, Johnson noted that while it's going "a little slower than in the past, I attribute that more to the market and the economic environment than I do to MRLS."