Endophyte-Infested Fescue: Hidden Dangers
When it first arrived on the scene in the United States during the early 1940s, tall fescue was considered a wonder grass. It was easy to establish, it was a good forage yielder, and it was tolerant of a wide range of management regimens. In short, it was a very tough grass that could stand heavy grazing and a high rate of animal foot traffic under a variety of climatic conditions and still continue to flourish.
Acre after acre was planted with tall fescue until its lush greenery covered some 35 million acres in the United States. However, problems soon began to be observed in animals grazing these lush pastures and fields. Horse breeders noticed that they were having foaling problems with some mares which were grazing fescue grass or being fed fescue hay. Cattle producers reported that steers on fescue pastures or being fed fescue hay appeared to be unthrifty and that milk production in lactating dairy and beef cows was reduced.
The livestock and equine industries turned to science for some answers. They came in the late 1970s.
A fungal endophyte was discovered that can have serious deleterious effects on animals consuming it. The scientific name for the fungal endophyte is Acremonium coenophialum.
Its effect on pregnant mares can be severe. Mares grazing on infected fescue pasture or fed infected fescue hay might have prolonged gestation, a tendency to abort, development of an abnormally thick and/or tough placenta, a retained placenta after giving birth, difficulty giving birth (dystocia), or no milk for the foal once it is born--if, indeed, the foal is born alive and remains alive after birth.
In addition, mares which have been grazing infected tall fescue often do not exhibit the normal visual signs of impending birth. There might be little udder development, swelling of the vulva, or other signs that birth is imminent.
Endophyte infected tall fescue also often has a deleterious effect on a mare's fertility during the breeding season.
What Is This Fungus?
There are characteristics of the endophyte concerning its survival and growth that are significant. First of all, the fungus lives within fescue plants and does not affect the appearance of the grass, thus successfully hiding itself from science's probing eyes for some years. The fungus is transmitted only through the seed. It is not harbored in the soil and does not spread from plant to plant.
A laboratory analysis is required to detect its presence. A sample of fescue that is to be examined for fungal infection is obtained by collecting stem tissue at random from throughout the field. Laboratory personnel examine each stem to determine whether it is infected. Thus, they can arrive at an approximate percentage of plants infected in the pasture.
The level of infection in existing fescue pastures varies widely, but most old fescue stands in the United States are infected, usually at levels of 70% or more of the plants in the pasture.
The good news is that an endophyte-free fescue grass has been developed. The bad news is that it is difficult to eradicate the infected grass. The infected seed is actually more hardy than its non-infected counterpart. Infected plants can survive adverse conditions that would result in the demise of non-infected plants.
For horsemen, science has provided several bits of good news. First, it has been learned that removing mares from infected grass 30 days before foaling will eliminate the endophyte's harmful effects. Second, a medication has been developed that appears to negate the harmful effects if administered to the mare on a daily basis for 10 to 15 days prior to foaling. More about that later.
First, some background about the endophyte and the research that has yielded the information we have before us today.
The man credited with discovering the endophyte is Charles Bacon, PhD, a plant pathologist for the United States Department of Agriculture at the Richard Russell Research Center in Athens, Ga. The year of his breakthrough discovery was 1977.
In the wake of that discovery came research aimed at documenting the detrimental effects of what became known as fescue toxicity. The first research involved the effects of infected fescue on cattle. Early studies were carried out at Auburn University and provided a clear indication that infected fescue did, indeed, have harmful effects on cattle consuming it as either pasture grass or cured hay.
Further research conducted during the 1980s showed that the reproductive efficiency of cattle also could be reduced by the endophyte. Furthermore, milk production of cattle grazing infected fescue was found to be markedly reduced.
Then came a study that began in the fall of 1986 at Auburn University which was partially funded by the American Quarter Horse Association. It established in convincing fashion that the endophyte is responsible for a number of reproductive difficulties in pregnant mares. That particular study was headed by Marshall R. Putnam, DVM, MS.
Following is an account of that definitive study:
Four research pastures of 11 acres each were established on a College of Veterinary Medicine unit at Auburn, Ala., in the fall of 1986. Two of the pastures were endophyte-free, while the other two had more than 80% endophyte infection. Both the infected and non-infected grass were Kentucky-31 tall fescue.
Once the pastures were established, nitrogen was applied in February and again in September at the rate of 100 pounds per acre at each application.
Twenty-two mares were involved in the study. Of that number, six were Thoroughbreds, eight were Quarter Horses, seven were Arabians, and one was a Morgan. The mares were bred on synchronized estrous cycles from June through August of 1987.
After pregnancy had been confirmed by palpation, the mares were randomly placed on either infected or non-infected fescue pasture on Oct. 1, 1987.
The mares remained on the same fescue pastures through foaling and during the immediate post-partum period. During the winter, when grass growth in the experimental lots did not provide enough forage, the horses were fed either infected or non-infected fescue hay in accordance with the status of the pasture to which they had been assigned--the mares on the non-infected pastures were fed non-infected hay while those on the infected pastures were fed infected hay. The hay was produced in fields planted at the same time and from the same seed lots as the research pasture.
The results were dramatic. Of the 11 mares which had grazed infected fescue pasture and had been fed infected fescue hay, 10 had obvious clinical dystocias (foaling problems). Four of the 10 mares had to be euthanized. Two of those four suffered severe uterine rupture; one had unresponsive posterior paralysis; and one was put down because of complications due to a Caesarean section.
The infected fescue also severely affected foal survival. Of the 11 foals whose dams were exposed to the fungus, only one survived. Three died soon after birth; one died during delivery; another survived for several hours, but was euthanized when it did not respond to routine nursing care; and a third lived for seven days, but did not respond to aggressive nursing care and succumbed to septicemia despite plasma transfers and supportive care.
Of the seven stillborn foals first observed during assisted labor, the researchers reported, death apparently occurred during the birthing process.
In 10 of the 11 mares on infected fescue, there was no evidence of udder development or lactation prior to and through parturition.
Now for the dramatic difference for the group of mares on non-infected fescue. All mares had a normal birthing process, all mares produced normal quantities of milk, and all foals survived.
In addition to the catastrophic birthing problems for mares on infected fescue, the researchers also noted that these mares demonstrated some clinical responses. They had intermittent loose feces and two had diarrhea throughout the period. In addition, they sweated earlier in the day and more profusely than the mares on non-infected fescue.
The problems associated with fescue, unfortunately, go beyond the final stages of pregnancy and parturition in horses.
J. P. Brendemuehl, DVM, PhD, Diplomate ACT, formerly at Auburn University, where he was one of the leading researchers in the ongoing fescue toxicity study, and now at Tuskegee University in Alabama, has reported that ingestion of infected fescue can have a detrimental effect on fertility and embryo survival.
Here is what Brendemuehl had to say in the wake of that particular research project:
"Mares grazing endophyte-infected fescue pastures have a significant delay in return to cyclicity during the spring transition. The number and size of follicles were significantly lower and smaller in January, February, March, and April in mares grazing infected pastures. The time to first ovulation was likewise significantly delayed, with the first ovulation not occurring until May 28, compared to April 15 in mares grazing non-infected fescue. The delay of approximately 43 days represents a loss of over two breeding cycles from the breeding season. Particularly in older or problem mares, this delay could result in a lost year of productivity.
"My co-workers and I compared the effects of grazing endophyte-infected fescue on cyclicity, pregnancy rates, and embryonic death rates. Mares grazing endophyte-infected pastures demonstrated prolonged luteal function, decreased per cycle pregnancy rates, and increased embryonic death rates compared to those grazing endophyte-free pastures. Continuous grazing of endophyte-infected fescue during breeding resulted in a 45% pregnancy rate at 14 days compared to 75% in mares grazing endophyte-free grass. At the end of a 60-day breeding period, the same percentage of mares were pregnant in both groups. A great incidence of prolonged luteal activity was observed in non-pregnant mares grazing infected fescue.
"Early embryonic death was observed in 30% of mares grazing endophyte-infected fescue compared to approximately 10% of mares grazing endophyte-free pasture. Embryonic development based on vesicle height at Day 14 after ovulation was not different between groups for embryos that maintained viability.
"Embryos that underwent early embryonic loss were small at Day 14 or were irregular in shape. Plasma progesterone concentrations were greater at 21 days post-ovulation in endophyte-infected mares in which the embryo remained viable than in endophyte free mares that experienced early embryonic death or that demonstrated prolonged luteal activity."
Brendemuehl summed up the results of the study this way:
"Grazing endophyte-infected fescue can have a detrimental effect on reproductive efficiency due to a delay in initiation of ovulation, an increase in cycles bred per pregnancy, prolongation of luteal function, and increased early embryonic loss.
"When mares must be maintained on endophyte-infected fescue pastures during breeding, repeated examinations to diagnose and monitor pregnancy maintenance are necessary. Weekly or bi-weekly examination between Days 14 and 40 is required to identify mares that have undergone embryonic loss or prolonged luteal function to maximize reproductive performance.
"Clearly, as in the other species examined, grazing pregnant mares on endophyte-infected pastures can decrease reproductive efficiency."
Options For Grazing Fescue
About the only good news that surfaces from the research involving pregnant mares and infected fescue is the fact that the damage seems to be concentrated during the final days of pregnancy. If pregnant mares are removed from infected fescue pastures at Day 300 of the gestation period, the toxic effects are eliminated.
For some breeders, however, this may not be a practical approach because of space problems.
Today there is another option, thanks to research conducted by Dee Cross, PhD, of Clemson University in Clemson, S.C. Cross' research has resulted in a medication called domperidone. When it is administered for the last 10 to 15 days prior to foaling, it negates the toxic effects of infected fescue and mares usually can safely deliver normal foals and have normal milk production.
Before we can understand how the medication works, we first must understand just what happens in the mare's body during the last stages of gestation when she ingests infected fescue.
What Really Happens To Mares?
Brendemuehl and Cross explain the toxic reaction something like this:
The body of a pregnant mare produces a biochemical known as dopamine. It occurs naturally throughout the body and affects the function of glands, organs, muscles, and nerves.
Within the endophyte fungus are ergot alkaloids, which, in a sense, imprison the dopamine receptors in the mare's system.
The result is decreased production of both prolactin and progesterone. Prolactin, a hormone secreted by the pituitary gland, stimulates milk production. Progesterone is the key hormone involved in maintaining a normal pregnancy. When the ergot alkaloids effectively reduce the normal supplies of these two hormones, the mare fails to produce milk and things go awry within her reproductive system.
The result can be no milk for the foal and a whole host of birthing problems.
Domperidone, says Cross, decreases the interaction between ergot alkaloids and dopamine. The result is a normal production of prolactin and progesterone, which results in a normal foal, normal birth, and normal milk supply.
In fact, says Cross, his research has produced a bonus benefit. Mares which have been ingesting non-infected forage, but are still lacking in milk production, can benefit from treatments with domperidone.
If the medication is administered to mares in that category, beginning with the day of foaling and for five days thereafter, he said, there normally will be a significant increase in milk production. If the treatment starts after foaling day, additional treatments--up to 10--might be necessary.
Back to domperidone as a treatment for mares on infected fescue pasture. What, Cross was asked, is the success rate for the medication?
It is extremely rare, he says, for it to fail if administered as prescribed. In several hundred mares treated with domperidone, he says, virtually all had normal deliveries and the foals were normal. If the mare is left on infected pasture right up to foaling, Cross recommends that treatments begin 15 days prior to the expected foaling date. If the mare is removed from the infected pasture, treatment could begin 10 days prior to the expected foaling date. If, of course, the mare doesn't foal on the expected date, domperidone administration should be continued until she does foal.
Each treatment consists of between 4 and 6 ccs of domperidone--administered as one would a paste wormer--depending on the mare's weight. The cost, which can vary somewhat, is about $7 per treatment.
While the drug can be obtained by veterinarians, it is temporarily in a state of limbo with the Food and Drug Administration (FDA). Cross says he spent part of the week of Jan. 20, 1997, with officials in Washington, D.C., working on details for obtaining final FDA approval. He is hopeful final approval will be received in the near future.
Until that approval is received, Cross is unable to legally advertise, promote, or fully market the product.
In the meantime, the drug holds "compassionate use status." This means that it can be legally administered by a veterinarian to horses known to have ingested infected fescue. As a practical matter, Cross says, this means that a veterinarian can obtain the medication on request from a small company he has formed, Equi-Tox, Inc.
(Cross holds a patent for his specific application of domperidone for the treatment of animals which might be suffering from fescue toxicity.)
The company he has formed, he says, is a joint venture between him and Clemson University. Clemson has established a Center for Applied Technology. Its stated purpose is to help establish small companies to develop and market products that are a result of research at the university.
Domperidone falls into that category. Cross, in essence, purchased back from the university the technology he developed and formed Equi-Tox, Inc. In return, he will pay a royalty to Clemson University on all sales of domperidone. (Veterinarians desiring more information on obtaining the medication can contact Equi-Tox by calling 864-646-6443.)
Another bit of good news about domperidone, says Cross, is that it has no negative side effects.
Although domperidone is new as far as its use for treating fescue toxicity is concerned, it has been around for some time. It originally was used in dogs to control vomiting.
Though not approved for human use in the United States, it is used in other countries to control vomiting
in humans, including that associated with chemotherapy.
Where Is The "Bad" Grass?
A matter of concern that arises when discussing infected fescue is just where it might be found geographically. There is no definitive answer, other than the fact that it is widespread in this country. While infected fescue is generally considered to be a problem in the East Central and Southern United States as well as the Pacific Northwest and California, Cross is of the opinion that it is present in many other states, including the Midwest and Rocky Mountain regions.
Cross says he recently traveled across South Dakota and was surprised by the amount of fescue he observed in pastures throughout the state. Montana, he says, also has become aware of a problem with infected fescue.
Unfortunately, he says, lack of awareness in some of these areas has lulled horsemen into a feeling of complacency. They, quite simply, haven't identified fescue--infected or non-infected--that might exist in their pastures.
As mentioned, the only way to determine whether fescue is infected is through laboratory testing. Auburn University, for example, offers a testing service for a $25 fee. It is available to anyone, no matter where they are located. (The fee for Alabama residents is $15.)
Individuals who want to find out which testing lab is closest to them would do well to contact the office of the agricultural extension agent in their area.
Getting Rid of Infected Fescue
One of the solutions for the fescue problem has been provided by science through development of an endophyte-free seed. However, it is no easy solution. Unfortunately, the contaminated strain of grass is just plain more hardy than the non-infected strain, and good management and much effort are required to eradicate infected fescue.
The contaminated seed is difficult to eliminate for a number of reasons. One example, reported in a publication funded by the Oregon Tall Fescue Commission and prepared by Auburn researchers, is the fact that infected plants are more resistant to insect feeding than are non-infected plants.
Several years ago, according to the report, scientists in New Zealand found that the Argentine stem weevil would devastate endophyte-free rye grass, but not infected rye grass. The Argentine stem weevil is not a pest in the United States, but this knowledge, the report stated, is of concern because the endophyte in rye grass and fescue are closely related.
It was also reported that greenhouse and environmental chamber work at several locations has shown that some insect species prefer and/or develop more rapidly on endophyte-free fescue. Studies carried out in Kentucky provided evidence that alkaloids in infected fescue are associated with increased resistance to insect feeding. A greenhouse study in Alabama revealed more than three times as many spiral nematodes (a type of pest) associated with the roots of endophyte-free plants than of infected plants.
The vigor of infected fescue plants changes somewhat with geographic location. The further south one gets, says Cross, the more hardy the infected plants become in comparison to non-infected plants.
The report from Auburn via the Oregon Tall Fescue commission corroborated that assertion. In stressful environments in Louisiana and Texas, both described as marginal areas for growing tall fescue, stand loss was greater in established non-infected pastures. Infected fescue also was reported as being more drought resistant than the non-infected.
"Drought tolerance," the report stated, "seems to be associated with EI (endophyte-infected) plants having improved osmotic adjustment, greater sugar accumulation, better root growth, and more leaf rolling to conserve water.
"These findings have important implications. First, while fescue is regarded as a forage crop which is easy to establish, that may be less accurate when the fescue is EF (endophyte-free). Thus, when planting EF fescue, a producer should carefully follow all establishment recommendations. Overgrazing of EF fescue should be avoided, especially during the establishment year. Fields to which endophyte-infected fescue is only marginally adapted should not be planted to endophyte-free fescue.
"Experience has shown that if overgrazing, severe drought, or other highly stressful conditions occur, endophyte-free fescue will not persist as well as endophyte-infected fescue. However, endophyte-free fescue stands at the Auburn University Black Belt Substation have persisted and remained non-infected for over 15 years, though separated from infected fields by only a barbed wire fence. Despite the need for higher management levels, the opportunities provided by endophyte-free fescue are great."
One of the keys to establishing a good stand of endophyte-free fescue, the researchers point out, is to pick the right variety of non-infected fescue for a given region. University trials in the various geographic areas are a good source of variety information.
Once the non-infected seed is planted, the goal, obviously, is to prevent later establishment of volunteer infected plants. Any infected field that is to be replanted should not be allowed to produce seed during the establishment year, the report states. Seedhead formation should be prevented by heavy grazing, clipping, or chemical application.
Under usual storage conditions, the endophyte will die in seed within one or two years. Unfortunately, there is a downside to long-term storage. The germination level of fescue seed can drop sharply when it is stored for a long period of time, depending on such factors as temperature and humidity conditions. In addition, the vigor of seedlings resulting from planting old seed is likely to be reduced.
The Auburn researchers in their report for the Oregon Tall Fescue commission offered these methods for replacing stands of infected fescue.
Rotation--Rotating with other crops, followed by planting endophyte-free seeds, is deemed an excellent approach. There are many options, ranging from no-till corn or a summer annual forage such as pearl millet, to longer term rotations involving a perennial such as alfalfa or two or three annual crops.
Prepared Seedbed--Certain situations permit destruction of the old sod through tillage, preparing a seedbed, then replanting endophyte-free fescue. However, it is often difficult to completely destroy old fescue by tillage.
Chemical Kill No-Till--Where the above two methods are not feasible, chemical kill of infected fescue followed by no-tillage planting of non-infected seed is the only remaining option. This technique can be used to go directly from infected to non-infected fescue, or other forage crops can be used in a rotation.
It is critical that chemicals be used effectively, thus killing all of the existing infected fescue. In some cases, there might be common Burmuda grass or other species that must also be killed, requiring the use of more than one herbicide or a higher herbicide rate. Effective sod kill requires attention to label instructions and striving for optimum environmental and plant conditions that will permit greatest chemical effectiveness.
Best results from no-till tests, say the researchers, have been found with late summer or early autumn seedings of fescue, except in the northern fescue belt, where spring seedings are feasible. Although chemical kill has been satisfactory in the spring, they say, summer drought and weed competition often reduce stands of spring-seeded fescue.
A particularly effective approach, they suggest, is to use no-till plantings of annual forages after killing infected fescue. For example, infected fescue can be chemically killed in the spring and a summer annual grass can be drilled into the killed sod, followed by no-till planting of non-infected fescue seed in the fall.
Similarly, fescue can be killed in the fall, followed by sod planting of winter annuals and, if desired, sod planting of a summer annual grass the next spring.
Use of annuals in this manner "smothers" fescue plants that were not killed. It also reduces the likelihood of insects in the old fescue sod damaging young fescue seedlings.
Detriments in Performance Horses?
While the detrimental effects of infected fescue in the latter stages of pregnancy on mares and the foals they are carrying has been well documented, it is not known just what effects infected fescue has on perform-ance and pleasure horses that are not pregnant and are not being bred.
Research has shown that in the case of cattle, there is a reduction in growth and a rough appearance in animals grazing on infected fescue. Could the same be true of horses? More research will be required before a definitive answer can be given.
There is no doubt that infected fescue has been responsible for millions of dollars of loss to the equine industry. The good news is that research has paved the way to negate the harmful effects of infected fescue and has shown landowners how to rid themselves of the problem.
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: University Equine Hospitals