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Fescue Under Fire

Written by Breanne Hill on .

Image    Since the first equine tasted its first mouthful of roughage, grass has been a natural food source for the animal we call horse. In fact, horse owners are so comfortable with the concept of grazing that they use turnout time in a velvety-green pen as reward for a job well done, and there is an almost universal “happy horse retirement” image of good old “Sugar” chomping away on the back forty, while a rainbow shines in the background and birds twitter in the trees.  
    However, as is the case with most dream scenarios, the reality of the horse/pasture relationship is much more complicated than the perception. There are many different types of grasses and several scenarios in which these grasses can become compromised, creating roughage that has the potential to cause severe health problems if ingested by a horse.     Perhaps one of the most feared and documented among these pasture problems – especially during breeding and foaling season – is the relationship between the grass called fescue and Neotyphodium coenophialum, an endophyte fungus.
    Fescue that is infected with this endophyte fungus is a dangerous food product. In particular, it is poisonous to late-term pregnant mares. The toxin, or alkaloids, produced in endophyte-infected fescue can penetrate a mare’s system, resulting in such complications as a prolonged gestation period, lack of milk production, stillbirths and birthing complications that may be fatal for both mare and foal. Additionally, if a foal survives a toxic pregnancy, it may be underweight with hooves and teeth that are not fully developed or it may have neurological problems—all in all, scary situations for horses and their owners.
    Until recently there have been very few defenses to the endophyte fescue risk, but researchers at Mississippi State University are devoting their time to changing this.
    Headed by Dr. Peter Ryan, an associate professor of animal and dairy science, MSU has been conducting tests on the effects of endophyte-infected fescue on all breeding stock, including younger horses and stallions. Now they believe they are close to helping approve new cultivars of endophyte fescue that will not negatively affect horses. These fescues have been dubbed “endophyte friendly,” and MSU is hoping the name rings true.

Pretty poison
    Fescue grasses are European in origin. They were brought to the United States in the late 1800s because of their heartiness. In short, they don’t succumb to instances of drought and overgrazing, as do some grasses native to North America.
    In the 1930s, 40s and 50s, fescue enjoyed a boom in popularity due in no small part to the frenzy of replanting that occurred following the harsh Dust Bowl years. Thanks to the Dust Bowl scare, vigorous fescue found a permanent home in the agricultural centers of America’s heartland.
    Unfortunately, it was later found that fescue’s attractive qualities were in direct relation to endophyte infection. Endophyte is a fungus that lives its entire life cycle inside of grass. Transmitted by seed only, it does not harm grass, nor does it distort the plant’s appearance. It can’t even be detected without laboratory analysis—a measure many have had to take to see what “kind” of fescue they have growing in their pastures.
    “Endophyte-free fescue cultivars do exist, but they are not as persistent as the endophyte-infected cultivars under harsh conditions such as Kentucky 31,” Ryan said. “The problem is they don’t survive very well in the agricultural regions of the Southeast and Midwest. A drought or extreme heat kills them and you have to reseed. Even as far north as Kentucky, they may not survive.”
    Fescues infected with endophyte, however, benefit from nitrogen trapping and stronger roots. They are also less palatable to animals and, therefore, less likely to fall victim to overgrazing.
    “It’s nature’s way of preserving the forage,” Ryan said. “A lot of plants will do that to prevent overgrazing by herbivores [i.e., cattle, horses]. Now animals will eat these plants, but they’ll only eat a certain amount.
    “Of course, if you have nothing but endophyte-infected fescue in a pasture and horses are hungry, that is what they’re going to consume because they have no choice.”
    Currently, in the United States, endophyte-infected fescues are found predominately in the Pacific Northwest and in the Southeast. They are also prominent in the so-called “transition zone,” which includes Oklahoma, Arkansas, Missouri, Tennessee, Kentucky, Virginia and northern parts of North Carolina, Georgia and Texas.
    “The growth of fescue is very dependent on the season,” Ryan said. “If you have a very mild spring or a warm spring with a lot of rain, the stuff grows like gangbusters, which is why it thrives where it thrives.”
    The level of toxicity a horse can reach by eating endophyte-infected fescue is also reliant upon the pasture and environmental conditions conditions.
    “A lot of people want to know, ‘What is the toxic level of the infected grass?’ ” Ryan said. “The thing about toxic levels is they’re dependent upon how heavily contaminated your pasture is—which is basically how much grass you have—and how long the mare is in the pasture.
    “Usually, if the mares are out all day in the spring months, and depending on their consumption level [weight versus amount of contaminated forage consumed] – which is one way of assessing level of toxic exposure.”

The program
    MSU’s fescue research program has a straightforward, simple set up. The university maintains six separate pastures at the Mississippi Agriculture and Forestry Experiment Station in Starkville of about eight to 12 acres each for its fescue research. Of these pastures, two are seeded with toxic endophyte-infected fescue, often referred to as wild type endophyte-infected fescue. It is in these pastures that Ryan and his team have observed the cruel effects that toxic fescue can have on late-term pregnant mares.  
    “The alkaloids produced by the endophyte-infected fescue may interfere with normal endocrine functions,” Ryan said. “These alkaloid compounds at high enough exposure levels may interrupt normal pregnancy and may lead to serious labor problems.”
    During their research, the MSU team has witnessed mares that don’t lactate and mares who miss their due date and end up delivering so late that they experience problems during labor.
    “That’s one major consequence of fescue toxicosis during late pregnancy in the mare,” Ryan said. “They don’t deliver at their due dates. They can extend out to a fairly prolonged period of time and that creates a situation where a mare is trying to deliver a larger-than-normal foal. We’ve lost both the mare and the foal in that situation.”
    Ryan has also seen several “dummy” foals born due to toxic fescue complications.
    “Toxic fescue can disrupt the normal function of the placenta,” Ryan said. “So, the foals may not receive adequate oxygen in utero and  may be born with basic brain-function problems.”
    To address this concern the MSU research team is investigating the merits of grazing pregnant mares on non-toxic (friendly) endophyte-infected fescue pastures. Two pastures at the Mississippi State University Experiment Station have been seeded with AGRFA 144, a new endophyte “friendly” fescue – endophyte friendly meaning it should retain the strengths of endophyte-infected fescue without producing the toxin that is a danger to animals.
    AGRFA 144 research trials have demonstrated that this cultivar is safe for consumption by cattle, but, with the backing of the Noble Foundation of Oklahoma, it is MSU’s job to help prove that AGRFA 144 could also be successful in horses.  
    “Cattle and horses are affected by toxic fescue in different ways,” Ryan explained. “Cattle are more prone to vascular constriction leading to loss of peripheral circulation, resulting in necrotic ears, shedding of hooves and metabolic problems.
    “Horses suffer more serious pregnancy-related problems and hormonal disturbances, so you’re dealing with very different problems. That’s why we have to do separate research trials for horses.”
    Last spring, the school turned eight of its 50 research broodmares out on its new AGRFA 144 pastures for approximately six weeks. There was only one complication that resulted from the research – the lack of the fescue itself.
    “We didn’t see any adverse response in the horses,” Ryan said. “But we weren’t sure we could really go to the bank with that because we were in the midst of a drought and didn’t get as good a growth of the fescue as we wanted. Thus, it was difficult to determine for sure whether the positive outcomes were entirely due to the novel endophyte-infected fescue.”
    This year, however, is a different story. The fall growing season has been kind to Mississippi, and Ryan feels that the pastures should have acceptable levels of fescue for research beginning in late February or early March.
    “We’re going to put a half dozen mares on each of the test plots,” Ryan said. “They will be out there 24/7 until they foal.”
    While the mares are on the new fescue, they will be strictly monitored. The researchers will draw blood from the broodmares approximately three times in the course of a week. The blood tests will help the researchers evaluate hormonal changes, changes in the immune system caused by stress and any kind of toxic effects. In pregnant mares, they will also assess progesterone – the hormone of pregnancy, evaluate the placenta using ultrasound and determine degree of mammary gland development. Urine will be assessed to determine levels of alkaloid toxin exposure.
    “In late-term pregnant mares, the toxins from endophyte-infected fescue can affect many factors associated with late pregnancy,” Ryan said. “So, we pay close attention to several physiological parameters for a sign of problems.”
    Ryan estimates that it will take two years, or two springs, worth of such research before AGRFA 144 can be marketed to the public as being a safe alternative endophyte-infected fescue to the wild type toxic endophyte-infected fescue for horses.
    “I think if we get this season in and then next season, that would be pretty good,” he said. “You couldn’t really do it in one year because they would say, well that might have just been a freak year. But I think once we do the two years and don’t see any adverse changes in their blood chemistry or endocrine profiles, and they’ve foaled out normally, it will be presented to the horse-owning public.”

Fight it now
    Most horse owners would be surprised to know that fescue has been shown to not just affect the biological conduct of late-term broodmares, but also the fertility of horses in general.
    For example, in the 1990s Ryan said research showed signs that toxic endophyte-infected fescue was associated with early term embryonic loss in mares and affecting their ability to become pregnant again. What’s more, in the last year MSU has received calls from Horse Farms in Kentucky that were reporting a high number of early term losses. The mares in question had access to toxic fescue.
    “Some of the farms are beginning to pay more attention to the problems associated with grazing mares on toxic fescue, and they’re starting to notice more instances of embryonic loss in early gestation,” Ryan said. “And this is happening in pastures that are more heavily infected with fescue than not.”
    And then there are the stallions. A few years ago, MSU studied the effects of endophyte-infected fescue on eight stallions, feeding them contaminated fescue seed in their daily rations in a short-term trial.
    “We didn’t see major changes in their reproductive function,” Ryan said. “But we did see some neuroendocrine (nerve cells that produce hormones) changes, and that’s very important because that’s never been shown before. We’re still in the early stages of this area of research.”
    Ryan said that a great deal of research will be conducted in the future on the effects of toxic endophyte-infected fescue exposure in all types of horses.
    In the meantime, and until more cultivars of endophyte-friendly fescue seed are approved and made available to the public, horse owners will have to continue to take their own precautions against the dangers of fescue toxicosis. For starters, if you suspect your pasture is infected with toxic endophyte-infected fescue, call your local agricultural extension office. The office should send out a representative to take a samples of the pasture forage for testing—again, due to the nature of endophyte, lab testing is the only way a grass can be found to be infected with the fungus.
    If it is discovered that your pasture is infected with toxic endophyte-infected fescue, you still have a few options that may help ensure your mare has a healthy pregnancy and foaling.
    First of all, be sure to remove your mare no later than day 300 of her pregnancy. Removing a mare from an endophyte-infected pasture will clear her system of toxins within 24-48 hours but the effects may persist for some time after. From there, place her on non-fescue pasture, in a stall or in a dry lot with proper nutrition. Some veterinarians recommend that you remove your mare 60-90 days before the mare’s anticipated foaling date.
If a mare cannot be removed from toxic fescue pastures, another option may be to place her on domperidone, (as) an oral paste. However, owners should first consult with their veterinarian as to the appropriateness and timing of the commencement of this treatment.
    Of course, the best defense against toxic endophyte-infected fescue is to keep your breeding stock away from it completely – if you have that option. If you don’t, or if your broodmare is already past her 300th day of pregnancy, consult your veterinarian for guidance.

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