Managers Doing Good Job with Pastures

A week following the Dec. 23 release of information about the University of Kentucky’s pasture monitoring related to mare reproductive loss syndrome (MRLS), Jimmy Henning, PhD, extension forage specialist at the University of Kentucky (UK) discussed some of the findings. There are some “real positive things” contained in the report, he said; the most important was that “we know a lot more about what is normal” in Kentucky pastures.

“For example, we know we can have cyanide in white clover, but it’s not that much, and it’s not a real problem,” he said. “We know the mineral content (of forages) during weather changes.”

But, he added, the testing won’t end with one season, and monitoring will continue in 2003.

One of the things that the agronomists learned is that the grasses normally found in Kentucky are not changed that much by weather, and that horse managers have done a good job managing pastures. So, while the weather has an indirect effect on MRLS, it’s more coincidental due to the presence of Eastern tent caterpillars (ETC) in pastures than the weather itself. “If there were no Eastern tent caterpillars and the same weather, there would be no problems,” he said.

“The mycotoxins still have some people bothered,” added Henning. That is because samples are “dirty” (contaminated) and the assays are very sensitive. The good news is that when mycotoxins were found, they were found in low levels, he added.

On the topic of fescue and endophyte infection, Henning said, “Not surprisingly, tall fescue can have high endophyte levels in pastures certain times of the year. Perhaps that tells farm managers to pay a little more attention to tall fescue. Test it to see if it’s infested. Treat late-term mares with Domperidone.”

(Endophyte-infected fescue can cause early placental separation or “red bag” delivery of foals; prolonged gestation; and agalactia or lack of milk production. For more on endophyte and fescue see "Fescue Field Management".)

Perennial ryegrasses (especially the Linn variety) are sold in Kentucky and can be infected with endophyte. Henning said that when he discovered last year that some of the varieties were infected, he went to distributors and growers of the seed and said that if it were to be sold to horse farms, it needed to be endophyte-free. “I’d been told that type of ryegrass was endophyte-free,” said Henning. “That’s a biggie for pasture management, but might be far down the list (as a cause of) MRLS.”

Henning said the agronomists and entomologists at the University of Kentucky are tracking ETC egg masses this winter to try and predict the caterpillar population in 2003. He said some of the monitoring of pastures next year will be correlated with the stages of the caterpillar’s growth.

“As a group, we are trying to find out what about the caterpillar is toxic,” said Henning. “Is it a virus or bacteria or something in the skin? We need to know that because at some point we want to be able to go out into a pasture and sample it and say it is safe.”

He said as far as what this surveillance has to offer to farm managers, it’s that if they control Eastern tent caterpillars in the tree and they never wander, the pasture is sound (safe) for horses; if caterpillars are crawling through pastures, there needs to be a way to know if they left something behind. Henning added that agronomists have learned more about pastures, and know that managers have done a good job.

When asked about any correlation with pastures and the fall reproductive losses, he said that while researchers at the University of Kentucky are treating this as a “deadly serious” problem, he said no one has shown him a correlation with MRLS to this point. “I’m not convinced that it’s MRLS-related,” said Henning. “We do know that in the fall the tall fescue grows a lot, and that if a mare was challenged early in the year (with something associated with MRLS), could the fescue be enough to trigger an abortion?”

Henning and his associates are far from on vacation during the winter months. They have collected numerous samples and have them in storage and will continue testing into the new year. “We’ve got a freezer with about 500 pounds of frozen grass; that’s about the size of 10 bales of hay,” said Henning.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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