Fescue Field Management
It is estimated that 35 million acres of United States pasture are planted with tall fescue (Festuca arundinacea), and roughly 700,000 horses graze these fescue pastures. This plant is a cool-season plant, so it grows in cooler climates, is tolerant of poor drainage and poor soil, and has a good regrowth after grazing. It also lasts longer into cool weather than many species, helping to extend the grazing season as long as it is allowed to regrow in the late summer or early fall, and thus saves money on hay and grain.
A Plant Within a Plant
Fescue can be a host to a type of fungus called an endophyte, a term meaning a plant within a plant (endo=within and phyte=plant). This endophyte, which grows between the cells of the plant, is called
Acremonium coenophialum or Neotyphodium coenophialum. The endophyte makes the plant heartier (more drought-resistant and insect-resistant), and enables the plant to have a good amount of regrowth. But this fungus that makes fescue so desirable for pasture maintenance also causes problems for livestock producers.
In the 1970s, researchers discovered an endophyte in fescue that caused a disease called fescue toxicosis. In an Auburn University experiment, scientists found a difference in health between steers grazing newly established stands of fescue and those grazing old pasture. They soon discovered that the thriving cattle were grazing endopyte-free fescue, and those not thriving were grazing infected fescue.
It was also discovered that the grass itself wasn't harmful to livestock; the endophyte produces ergot alkaloids (ergovaline is the primary one) that cause an elevated body temperature, low feed intake, and weight loss in all livestock. These symptoms are most prevalent in cattle, but Bayer Animal Health's horse health web site reports that this might also happen in horses.
In cattle, it causes a condition called "fescue foot," a swelling in legs and decreased circulation to the foot that causes hooves to detach and tissues to die.
The trouble with horses mainly lies with pregnant mares. If mares graze on fescue 60-90 days prior to foaling, a number of problems can occur--prolonged gestation, difficult birth (dystocia), thickened placenta, decreased colostrum production, and lower milk production. Mares often show false heats and have difficulty re-breeding. Worst of all, foals are often born weak or stillborn. Those which do survive often are somewhat unhealthy and need supplemental colostrum.
Fescue and Your Pasture
It's estimated that 90% of fescue fields in America are infected with the endophyte.
But does your pasture have endophyte- infected fescue? It's hard to tell without a lab test. You can't see the endophyte on fescue--it lives its entire life cycle inside the plant, and the fungus is only transmitted by seed. The endophyte level in your pasture can only be determined in a laboratory.
Samples need to be taken according to local laboratory requirements. You can contact your local agricultural extension service for information on how to take a sample and for an address of a testing lab near you, or send a sample to the Fescue Diagnostic Center, Plant Disease Laboratory, Auburn University, Auburn, AL 36849, along with a check for $25.
The good news is that infected fescue won't infect seed or plants that are endophyte-free. In fact, an endophyte-free stand of fescue at Auburn University's Black Belt Substation has remained so for 10 years, even though it is next to an endophyte-infected stand of fescue and only separated by a barb wire fence.
If you have an existing stand of fescue that is infected, nothing can be done to remove the fungus without killing the grass, including use of fungicides. There is a theory that storing seeds for at least 18 months can reduce endophyte levels, particularly if they are stored at high temperature and moisture. But the toxin might still be present, so storing seeds won't make the grass grown from it safe to feed.
Managing Horses Grazing Infected Fescue
For horse owners, the problem seems to affect breeding mares more adversely than non-reproducing horses. Microbiologist Kyle Newman, PhD, of Venture Labs in Lexington, Ky., recommends removing mares from the pastures during the last three months, or even for the entire gestation period. "Although there do not seem to be long-term effects in non-breeding animals, this remains to be seen." Right now, it is believed that horses can pass the toxin out of their systems within 30-45 days. For more information on the physiological effects of fescue, see "Hidden Dangers: Endophyte-Infected Fescue" in the March 1997 issue of The Horse, article Quick Find #735 at www.TheHorse.com; "Fescue Toxicosis and Treatment" in the July 2000 issue of The Horse, article Quick Find #208 at www.TheHorse.com; and "Fescue Toxicosis" in the August 1997 issue of The Horse, article Quick Find #647 at www.TheHorse.com.
Venture Labs is a contract research lab for the agricultural industry and Newman is one of the microbiologists monitoring the problems of early fetal loss and late gestation foal loss seen in Kentucky, Ohio, West Virginia, and other states in the spring of 2001. He says that although the main theory on the cause centers on the abundance of Eastern tent caterpillars and cyanide regurgitation, Newman says they are not ruling out fescue toxicosis as many of the symptoms are quite similar.
Scientists have created an endophyte-free fescue plant, but it has a few drawbacks. Because the endophyte makes fescue a stronger plant, the endophyte-free plant lacks most of the attributes of the infected fescue--it's not as drought-resistant, it has reduced summer survival, and since animals prefer the endophyte-free grass, it might be overgrazed. More pasture management will be required to maintain the endophyte-free pastures.
If you are concerned about the quality of your pasture and the level of endophyte infection, it might be better to re-establish the pasture using endophyte-free fescue or change to other grasses that don't have an endophyte problem. The first part of the re-establishment process is to remove the fescue. In most situations, this is done with herbicide applications to kill the grass. There are a number of ways this can be accomplished, and a visit to your county extension office for advice on what to do in your situation would be time well spent. In some cases, the pasture will be sprayed in the fall, and then another crop rotated on the land to help control any volunteer fescue that didn't die with the fall spraying. Re-seeding of the pasture can be done in the following fall. This re-establishment can take up to 18 months to develop a productive stand.
During the re-establishment year, it is important to not allow any of the fescue to produce seed, as this might become a source of infected plants in the new stand. Frequent mowing or close grazing of the grass during the growing season can prevent the formation of seed heads.
While at the county extension office, check to see what grasses would be most appropriate to use in the re-establishment of your pasture. There are many grasses to choose from, but make sure what you select is suitable for your situation. Using grasses other than fescue in your re-establishment will allow you to keep track of the volunteer fescue in your field. Remember that you can't tell the endophyte-infected fescue plants from the endophyte-free plants by looking at them. If fescue is a possible selection, make sure you use seed that is endophyte-free. This information is found on the seed tag.
Bayer's horse health web site includes the following suggestions for pasture management for horse breeders who have endophyte-infected fescue.
- Remove broodmares from infected fescue pasture 30 days before breeding and 60-90 days before foaling.
- Keep notes of when the mare was bred and when you think she'll foal. This way you'll know if she is late to foal, which is one symptom of fescue toxicosis.
- Let your veterinarian know how long your mare has been grazing the fescue.
- Watch the mare closely as her foaling date approaches, and alert your veterinarian if she doesn't develop signs of foaling.
- Keep the mare and foal off the infected fescue until weaning to prevent low milk production.
For more information on Fescue, contact the Oregon Tall Fescue Commission at 503-585-1157, online at http://forages.orst.edu/organizations/seed/otfc.
FESCUE FIELD GUIDE
You can recognize fescue in your pasture by its coarse- to medium-textured leaves and its distinctive bunch-like appearance. This grass normally grows to a height of 6-12 inches, though it can grow taller in ideal, non-grazed conditions. It has no rhizomes (horizontal underground stems that spread the plant stand), and the seedheads are open rather than clumped.
There are several varieties of fescue--tall, Kentucky 31 (a common type of tall fescue developed by Dr. E.N. Fergus of the University of Kentucky), red, and chewing. Tall fescue, particularly Kentucky 31, is the most popular grass for pastures. It's also used in silage, hay, and as a pasture grass.--Sharon Biggs
CONTROVERSIAL TREATMENT FOR FESCUE TOXICOSIS
Vivien Allen, MS, PhD, Thornton Distinguished Professor of Forages at Texas Tech University, and her colleague Korinn E. Saker, DVM, MS, PhD, Assistant Professor of Large Animal Clinical Sciences at Virginia Polytechnic Institute and State University, have been working on a study suggesting that copper deficiency triggers fescue toxicosis in cattle.
Their first idea was to administer a copper bolus. They later decided to take it one step further and fertilize the grass with Ascophyllum nodosum, a type of brown seaweed rich in copper and antioxidants. They found that with the fertilizer, the effect on the grazing cattle's health was remarkable--they were protected from the toxicosis.
"The turf work has shown repeatedly that we're getting this increased antioxidant activity and our suspicion--we don't have direct proof of this--is that this is what is affecting the animals' immunity," Allen said.
The research was published early last year in the Journal of Animal Science and included monitoring of 250 cattle over a span of three years.
Kyle Newman, PhD, of Venture Labs in Lexington, Ky., comments, "The actual conclusion that the seaweed provides some micronutrients in the form of antioxidants is, in my mind, a reach, as I don't think you can apply a cost-effective level of seaweed to soil/plants that would directly give you enough antioxidant taken up by the plant to be effective in the animal. There may, however, be some indirect influences on the plant that lead to improved antioxidant potential of the plant and/or the animal."--Sharon Biggs
MANAGING BREEDING MARES ON FESCUE
Removing a pregnant mare from pasture 60-90 days before foaling can be a financial and logistical difficulty for many breeders. Organizing and paying for stabling, bedding, hay, and making sure mares can get out into a non-fescue paddock for light exercise can be a daunting challenge. However, there is a glimmer of hope. Field trials conducted at Clemson Unive rsity from 1993 to 1997 with 1,236 mares left grazing on endophyte-infected fescue pastures throughout 33 states found that the drug domperidone, a specific dopamine-2 receptor antagonist, was found effective in reducing or preventing symptoms in 95.2% of the mares (treated with the drug anywhere from 10-30 days prior to foaling). Gestation length was near normal for treated mares, and 27 days longer on average for untreated mares. Udder development was normal and lactation was up for treated mares, while the opposite held true for untreated mares. The most impressive finding was that 93% of the treated mares had live foals, while 86% of the untreated mares delivered dead foals or foals which died soon after birth.
The reason why domperidone is so effective is because it reduces the effects of the ergot alkaloid produced by the endophyte in infected fescue. The alkaloid's dopamine agonists reduce milk production by reducing the normal production of prolactin (a protein hormone essential for milk production). Mares have difficult pregnancies because the hormone progesterone, needed for healthy pregnancy, is also inhibited.
Domperidone allows for near normal production of prolactin and progesterone , even in the presence of infected fescue, helping the mare to have a healthy pregnancy, a normal delivery, and proper milk production.
The downside to domperidone is that it can be expensive--around $8 a day. But compared to paying for extra feed and stabling and the all-around headache of managing a herd of pregnant mares in a stable or moving them somewhere else (or even losing the foal), the cost might be worthwhile. Talk to your veterinarian about what plan of action is right for your situation, and your mare(s).--Sharon Biggs
If you choose to feed fescue hay, understand that the toxins can remain in the hay for several years after cutting. Ask your feed supplier if the hay comes from an endophyte-free field. Then, before filling your loft, be sure by having some analyzed.--Sharon Biggs
About the Author
Sharon Biggs Waller is a freelance writer for equine science and human interest publications. Her work has appeared in several publications and on several websites, and she is a classical dressage instructor.