Tuesday, Jul. 23, 2024

From Fescue Fear To Fescue Understanding



As the farm manager for Mill Ridge Farm in Lexington, Kentucky, Marc Richardson attends the birth of 60 to 70 foals each year. When the phone rings, he heads for the foaling barn.

But in 2017, his first year overseeing foals instead of yearlings, those phone calls gave him an ominous feeling. “That year, any time the phone rang for a foal, I dreaded going,” he said. “You know, what’s going to happen tonight?”

During that foaling season, the farm, which was the birthplace of Kentucky Derby winner Giacomo, had broodmare after broodmare with problems. They had “red bag” cases, in which the placenta had partially or completely separated from lining of the mare’s uterus prior to the foal being delivered, mares with difficulty delivering, prolonged gestation and others with poor- quality colostrum.

“And we had a lot of mares that just weren’t producing milk,” Richardson said. “They had bags, but they weren’t making milk.”

Mill Ridge Mares

Broodmares at Mill Ridge Farm in Lexington, Kentucky, have experienced far fewer problems with foaling after the farm had their pastures tested by the University of Kentucky Horse Pasture Evaluation Program. Photo Courtesy Of Mill Ridge Farm

As the issues continued, the farm’s veterinarian, Stuart Brown, DVM, suggested that Richardson contact the University of Kentucky’s Horse Pasture Evaluation Program because the problems the mares were experiencing were classic signs of fescue toxicity. Fescue—a cool-season grass with heat, cold and drought tolerance—can be toxic and cause issues in late gestation for mares.

“When you’re sitting there, and you look at these big, beautiful, lush green pastures, you’re like, ‘We don’t have any problems; it looks great,’ ” Richardson said. “But nobody really knows until they test the fescue.”

The University of Kentucky Horse Pasture Evaluation Program, which began in 2005 and is free to the public, utilizes endophyte and ergovaline (the primary toxin produced by the endophyte) testing, as well as pasture species composition to calculate ergovaline in the total diet in broodmare pastures. This data is used to develop detailed management recommendations for individual pastures. The program has been growing in recent years, surpassing a goal of 20 farms a year, with a current count of 29.

“When we first started off, our biggest farm was maybe 60 acres, and now I do farms that have 60-acre fields,” said Krista Lea, the program coordinator for the UK Horse Pasture Evaluation Program. “But what I love about this program is that we can work with those big Thoroughbred operations that you see on the postcards, but we also work with those small sport horse breeders. And we work with boarding facilities, and we work with backyard horse owners, and owners that have no interest in breeding but still have interest in improving their overall pasture management.”

Mill Ridge, which has 900 acres, had all the mares there on a rotational grazing loop, which culminated with them moving to a pasture closest to the foaling barn. UK’s testing confirmed the final pasture had the type of fescue that caused issues in broodmares.

“That field was the worst field on the farm,” Richardson said.

Pregnant Mares And Fescue

Endophyte-infected tall fescue causes a host of problems in broodmares, from prolonged gestation to foaling difficulties to thickened placentas, including “red bag” emergencies and issues with milk production.

“Those are key things that I’m looking for when people are describing fescue issues,” Lea said.

Removing mares from endophyte-infected tall fescue 90 days before foaling has long been an effective management technique. But not all fescue is created equal, and not all requires broodmares to be moved.


“There’s really three types of tall fescue,” Lea said. “There is the toxic endophyte tall fescue, which is the one that we always talk about, and that’s the one that we assume we have. It’s incredibly rare for me to find a farm that doesn’t have it that didn’t actively plant something else. So, you can kind of assume that the default tall fescue is the toxic one.”

UK Researchers

Researchers from the University of Kentucky Horse Pasture Evaluation Program examine grass in a pasture as part of their sampling procedures. Photo Courtesy Of The University Of Kentucky

There are also tall fescues that do not contain the toxic endophyte. “And they’re perfectly safe, they just don’t survive very well on pasture, and so we won’t have them in a pasture more than a couple of years,” Lea said.

The last is the novel endophyte tall fescue, which is a newer type and desirable to have in a pasture. “They’re durable, like the toxic fescue, but they are non-toxic, like the endophyte-free [fescue],” she said. “That’s why they’re kind of the best of both worlds.”

As a pasture grass, fescue is popular because of its durability and drought tolerance. “Right now in Kentucky it hasn’t rained in five or six weeks, and fescue is the only thing that’s still green,” Lea said. “It has lots of resistance to disease, to drought, to insects, and to grazing. It does really well under heavy grazing.”

Fescue has good forage quality, palatability and decent nutrition. The issue arises when it becomes infected with the endophyte, a fungus that lives between cell walls.

“It produces some compounds that make the plants a lot tougher, that give it a lot more durability,” Lea said. “However, it produces those toxic compounds.”

The university’s program has been encouraging farms to plant the novel endophyte tall fescue, which has been used on cattle farms for over 30 years.

“It’s only recently been accepted into the horse world, and it’s a very slow acceptance rate,” Lea said. “But we are slowly convincing a farm here and a farm there to plan a little novel and see how it goes. And I really think that it can be a game changer for us. But I think that adoption rate is really slow because people are just so set on all fescue is bad. And the truth is, it’s not all bad.”

So You Want Your Pastures Tested. Now What?

As the farm manager of Endeavor Farm in Versailles, Kentucky, where 40 to 50 foals are born annually, Keith Haag is keenly aware of the dangers of fescue toxicity in broodmares. But until four years ago, farm managers didn’t have a true sense of whether its fescue was the endophyte-infected type. As a result, the farm managed the mare’s environment to protect them for the last 90 days before foaling.

Endeavor Farm Pic 2

Resident broodmares More For Me and Sally’s Curlin graze at Endeavor Farm in Versailles, Kentucky. Photo Courtesy Of Endeavor Farm

“When the mares get within a month or month and a half of their due date, they stay inside overnight so that we can keep an eye on them. And then they just get turned out in a small paddock during the day, and there’s not a whole lot of grass in those paddocks. They’re mostly eating hay during that time,” Haag said. “So that was really our method of controlling whether or not these mares were exposed to endophyte-infected fescue.”

Both Haag and his wife, Laura Haag, are graduates of the animal science program at the University of Kentucky, and they knew the university offered a pasture evaluation program. In the four years since they first reached out to Lea and had her team test their pastures, their pasture management has changed drastically.

“Before we used the UK Horse Pasture Evaluation Program, we were just kind of throwing darts at a dartboard. We always drilled seed every year; we always applied herbicide, but we really didn’t have any game plan. It was just kind of, you know, we hope it works,” Keith said. “You can visually see a difference between 2018, when we started using the program, and now. I mean, our pastures are green and lush, and there’s very little weeds that you can see out there. It’s a huge difference, especially in our smaller paddocks that see a lot of traffic.”

When a farm manager reaches out to the University of Kentucky to have pastures tested, Lea and graduate students begin by going to the farm to take samples. They typically take 20 samples per pasture, depending on the size of the farm.


“It can take as much as two weeks for a bigger farm to be sampled. But a lot of the smaller firms we get done in a day,” Lea said. “And then it takes us about another two weeks to get all of the data analyzed, to get the lab results back for the fescue analysis, put together a book and a report for them.”

At that point, they meet with owners and go over the results. Often, the owners are surprised by the results and didn’t realize they had a fescue issue.

UK Grid Test

Researchers from the University of Kentucky Horse Pasture Evaluation Program mark off a grid in a pasture to begin collecting samples of grass to evaluate for toxic fescue. Photo Courtesy Of The University Of Kentucky

“And that is where I’m always very surprised,” Lea said. “First of all, there’s this assumption that most of our pastures are Kentucky bluegrass, and that we have a little bit of fescue. And that’s just not true. The fescue is a major portion of our pastures, not just in Kentucky but really across the southeastern United States.”

The process also includes making recommendations to the farm owners to improve their pastures, which can be something as simple as encouraging them to do rotational grazing to allow pastures to regenerate or applying an herbicide to reduce weeds.

“For those that have broodmares, we talk a lot about fescue-mitigation strategies, and they may decide to move their mares to a different part of the farm that has a lower fescue amount in it. They may spray [an] herbicide that can remove fescue from the system,” Lea said. “Or they may decide to kill out a pasture completely and start over. And that’s a practice that’s really scary to people, but we’ve actually found it’s one of the most effective pasture tools that we have.”

While the university conducts ongoing research, Lea said the best information comes from being out in the field.

“I really think our biggest expertise is that we visit so many farms, and we see so many fields—in many cases again and again and again—that I think we learn more from actually seeing what happens when people are doing things,” Lea said. “You know, research studies, they can tell us a lot, but at the end of the day, if it doesn’t work in the real world, it doesn’t matter. But when I work with farms and see them actually applying our recommendations and seeing what works and what doesn’t, and then tweaking those recommendations, that’s probably where we’ve had the most impact on our program.”

At Mill Ridge, Richardson and his team killed off the pasture laden with the toxic fescue and replanted it with orchard grass, bluegrass and some rye grass. By the 2018 foaling season, they saw a complete turnaround.

“We went from having a vet come out for half the foalings the previous year, and that next year, I think that we had like one issue, and it wasn’t anything that was fescue related,” Richardson said. “We didn’t lose any babies or any mares. As soon as we got them off the fescue, it was just like turning on a light switch.”

Though they were still fescue shy after getting rid of the toxic fescue, the farm has since planted a bit of the novel endophyte tall fescue. “And we’ve actually got a lot of good grass coming up from it,” Richardson said.

Mill Ridge also has reviewed its foaling records for the years leading up to 2017, when it had so many mares with difficulties foaling. “There were quite a few problems the year before, not as many, but there were quite a few. For the last like five years before [2017] there were problems, but they were just increasing more and more each year,” he said. “Being part of the pasture program—just, it makes such a difference. “

While the program only serves Kentucky, Lea said there may be resources in other areas, such as a local extension service, which is often free, that could test pastures.

“I think it’s really important that people just understand what’s in their pastures and knowing what kind of effects it can have on their horses,” she said. “Whether it’s fescue, or it’s different species of grasses, or it’s weeds, I just think it’s really important to know what’s out there and know what you’re feeding them.”

This article first appeared in the December 2022 issue of The Chronicle of the Horse. Subscribers may choose online access to a digital version or a print subscription or both, and they will also receive our lifestyle publication, Untacked. 

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