THE TALL FESCUE ENDOPHYTE
Southern Regional Beef Management Handbook
Dr. Don Ball, Extension Forage Crop Agronomist, Auburn University
Dr. Garry Lacefield, Extension Forage Crop Agronomist, University of
Dr. Carl S. Hoveland, Professor of Agronomy, University of Georgia
Tall fescue (Festuca arundinacea Schreb.)
is the most important cool-season grass in the United States, providing
the primary ground cover on some 35 million acres. It is a versatile perennial
used to provide pasture and hay for livestock, for various turf purposes,
and for erosion control. Commonly referred to as simply "fescue," this
widely adapted, persistent grass is seed propagated, tolerant of a wide
range of management regimes, and it produces good forage yields. Laboratory
nutritive analyses of fescue compare favorably to those of many other cool-season
Fescue became popular as a forage grass
in the United States soon after the release of the variety "Kentucky 31"
in 1943. During the 1940's and 1950's there was phenomenal interest in,
and widespread planting of, this grass throughout the lower Midwest and
a large portion of the South. In much of the South, fescue filled a void
where no other cool-season perennial forage grass was adapted.
Unfortunately, this new grass was not
without its shortcomings. Its forage was of relatively low palatability
to livestock, and performance of animals grazing it was erratic and often
disappointingly low. In addition, some cattle grazing fescue occasionally
developed lameness and sometimes lost portions of their feet or tails during
fall and winter. The term "fescue foot" was used to refer to this serious,
although relatively infrequent, problem. Another problem noted was termed
"fat necrosis ," which involves the deposit of hard fat in the abdominal
cavities of cattle. Fat necrosis is associated with heavy application of
broiler litter or nitrogen fertilizer to fescue pastures.
In addition, cattle grazing fescue
often developed a chronic unthrifty condition, especially apparent during
the summer months. This condition came to be widely referred to by the
terms "summer syndrome,' "summer slump," "fescue toxicosis," or "fescue
toxicity." Furthermore, mares grazing tall fescue pastures often aborted,
produced stillborn foals, had thickened or retained placentas, or produced
an inadequate quantity of milk. For many years these problems remained
a mystery, despite vigorous research efforts.
Discovery of Fescue Endophyte
It was not until the mid-1970's that
an amazing discovery regarding fescue was made. USDA scientists in Georgia
associated an endophytic fungus with poor gains of beef cattle in an on-farm
situation, and this was subsequently confirmed in replicated research at
Auburn University in Alabama.
The terms "fescue fungus," "endophyte,"
"fungal endophyte," and "fescue endophyte," have all been used to denote
the organism in question. "Endo" (within) plus "phyte" (plant) means a
plant that lives within another plant. In this case, the plant (endophyte)
is a fungus, originally identified as Epichloe typhina and later renamed
Acremonium coenophialum. It is generally accepted that these terms refer
to the same organism.
Two characteristics of the endophyte
have great practical importance. First, the organism does not affect either
the growth or appearance of the grass, and it requires a laboratory analysis
to detect its presence. Second, it is seed transmitted and apparently not
transmitted in any other way. Thus, once a noninfected stand is established,
it can be expected to remain that way unless infected seed are introduced
into the pasture and become established.
Studies with animals consuming endophyte-infected
fescue have shown the following responses in comparison to animals grazing
non-infected fescue: (1) lower feed intake; (2) lower weight gains; (3)
lower milk production; (4) higher respiration rates; (5) higher body temperatures;
(6) rough hair coats; (7) more time spent in water; (8) more time spent
in the shade; (9) less time spent grazing; (10) excessive salivation; (11)
reduced blood serum prolactin levels; and (12) reduced reproductive performance.
Some or all of these responses have been observed in numerous studies in
dairy cattle, beef cattle, and sheep consuming endophyte-infected pasture,
green chop, hay and/or seed.
The initial steer grazing study at
Auburn University showed an 82% increase in average daily gain (ADG), and
a 42% increase in gain per acre with endophyte-free fescue compared to
endophyte-infected fescue (Table 1). Interestingly, gains were reduced
throughout the grazing season, and not just in the summer. Other grazing
studies with steers in Kentucky, Alabama, Georgia, Missouri, Texas, Tennessee,
North Carolina, and Maryland have also shown ADG's 50 to 100 percent greater
on low-endophyte as compared to high-endophyte tall fescue pastures.
Table 1. Grazing days, beef gain/acre, average daily gain, and gain/animal
of steers grazing A. coenophialum-infected and non-infected tall fescue
pastures, Marion Junction, Alabama 1978-82.
*Adapted from: C.S. Hoveland and co-workers. Steer Performance and Association
of Acremonium coenophialum Fungal Endophyte on Tall Fescue Pasture. Agron.
]. 75:821-824. 1983.
|Tall Fescue Pasture
||*Beef gain (lbs/acre)
||Avg. daily gain (lbs)
Presence of the endophyte affects grazing
livestock in many ways. In a Georgia study, steers on low-endophyte fescue
grazed 43 to 65 percent of the time between noon and 4:00 p.m., while steers
on high-endophyte fescue grazed only 5 to 21 percent of the time during
the same period. Steers moved from high- to low-endophyte fescue did not
resume normal grazing habits for 26 days, indicating a residual effect.
Mississippi State University workers found that the body temperatures of
cattle did not return to normal until 56 days after removal from infected
fescue. Other studies in Alabama and Kentucky have shown increased gains
and intake, as well as lower body temperatures, of steers consuming endophyte-free
seed or hay when compared to animals consuming infected seed or hay. Research
conducted in Kentucky revealed a 39 percent reduction in forage intake
and 37 percent decrease in milk production during summer in lactating dairy
cows consuming endophyte-infected fescue. In addition, these cows lost
weight, while animals consuming non-infected fescue gained weight.
Other Kentucky work showed that beef
cows had a 35 percent lower pregnancy rate when grazing highly infected,
as compared to endophyte-free, fescue pastures (Table 2). Similar responses
have been found in Missouri. Furthermore, researchers at Auburn University
obtained a sharp drop in pregnancy rates of replacement beef heifers grazing
infected fescue, almost in direct proportion to the level of endophyte
infection (Table 3). Several other studies have shown sharply reduced milk
production of beef cows grazing infected fescue.
Table 2. Pregnancy Rate in Beef Cows
N. Gay and co-workers, University of Kentucky, 1986 (3 years)
|Low Endophyte Fescue
|High Endophyte Fescue
Table 3. Effect of Fungus-Infected Tall Fescue Pastures on Growth
Reproduction of Replacement Beef Heifers at Two Locations (Black
and Tennessee Valley Substations) in Alabama, 1984-86*
*Adapted from: S.P. Schmidt and co-workers. Fescue Fungus Suppresses
Growth and Reproduction in Replacement Beef Heifers. Highlights
Agricultural Research Vol. 33, No. 4, Winter 1986. Ala. Agric. Exp.
Over 4,500 producer-submitted fescue
samples from 30 states and several foreign countries have been tested at
Auburn University, and approximately 90 percent had some level of infection.
The average infection level for pasture samples was about 60 percent with
a range of infection from 0 to 100 percent. The fungus is especially prevalent
in areas where Kentucky 31 is the predominant variety.
Since most fescue fields are endophyte-infected,
most producers who use fescue as a forage grass are not obtaining the level
of animal performance which would otherwise be possible. The relationship
between level of infection and animal performance among animal species
and classes has not been adequately studied. However, data from several
states suggest that each 10 percent increase in endophyte level can result
in a reduction of 0.1 pound in ADG of growing beef animals.
Research in many states has demonstrated
conclusively that the fescue endophyte is associated with negative effects
on animal performance. The mechanism is as yet unknown but a toxin is strongly
suspected. Regardless, the economic impact of this problem is immense,
perhaps exceeding $500 million annually in terms of lost beef gain alone!
Potential Adverse Aspects
New Jersey studies found that sod webworm
damage is greater on endophyte-free than on endophyte-infected, turf-type
fescues. Also, greenhouse work in Alabama and Kentucky has shown that aphids
prefer endophyte-free fescue. Tests in Louisiana and Georgia revealed that
survival, growth, and development of fall armyworm larvae fed endophyte-infected
fescue were reduced. Kentucky researchers found evidence that alkaloids
in endophyte-infected fescue are associated with increase resistance to
insect feeding. A greenhouse study at Auburn University revealed over three
times as many spiral nematodes associated with the roots and soil of endophyte-free
than with endophyte-infected fescue plants. Work in Arkansas showed significantly
fewer nematodes associated with endophyte-free fescue in field tests in
Endophyte infection has also been associated
with morphological and physiological drought resistance mechanisms in tall
fescue. In Georgia, endophyte infection seemed to decrease stomatal aperture
and gas exchange. Also in Georgia, trials with a single clonal line of
fescue that infected plants survived 40 days of severe drought stress,
while only 25 percent of endophyte-free plants survived. Under moderate
drought stress the same plants were observed to exhibit leaf roll if infected,
but not if endophyte-free. Infected plants were also observed to have thicker,
narrower leaves, which presented less surface area for evaporation.
Grazing livestock prefer endophyte-free
over endophyte-infected fescue. If given the choice, they will spend far
more time grazing endophyte-free fescue, and their intake will he greater,
thus requiring a lower stocking rate.
An apparent difference in vigor has
been observed between infected and non-infected pastures in some environments.
This has usually been seen only in new plantings, but in tests conducted
in stressful environments, stand loss was greater in established endophyte-free
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 endophyte-free. It appears
that greater attention to management is needed for endophyte-free fescue,
especially during the establishment year. Thus when establishing endophyte-free
fescue, a producer should carefully follow all recommendations, including
time of planting, fertilization, etc.
Secondly, since overgrazing is more
likely to occur when the endophyte is not present, endophyte-free fescue
requires a higher level of grazing management. In particular, overgrazing
should be avoided during the establishment year or in highly stressful
environments. Top growth should not be grazed or clipped shorter than 3
or 4 inches, especially during the first year.
In addition, severe stress may be more
likely to result in stand decline of established stands of endophyte-free
fescue. Thus, fields which are only marginally adapted to fescue should
not be planted to endophyte-free fescue.
Finally, while insects and other pests
do not currently limit the use of endophyte-free fescue, it is possible
that pest problems may be greater with endophyte-free fescue. It may be
advisable to monitor such pastures more closely in the hope of eliminating
any such problems before they cause serious damage.
Relatively little information is available
regarding long term stand persistence of endophyte-free fescue. However,
endophyte-free fescue stands established in 1974 at the Auburn University
Black Belt Substation have persisted and remained endophyte-free even though
separated from infected fields only by a barbed wire fence.
Based on current knowledge and experience,
endophyte-free fescue can be expected to persist well, with the exception
of plantings exposed to highly stressful situations. However, even if periodic
reestablishment became necessary, the improved animal performance on endophyte-free
pastures would easily justify reestablishing a highly infected field. Despite
the need for somewhat higher management levels, the opportunities provided
by endophyte-free fescue are great.
Strategies for Coping with the Endophyte
Livestock producers who have established,
or who plan to establish, fescue fields should develop an intelligent endophyte
strategy based on research findings. The following is a review of options
available for avoiding or minimizing endophyte effects.
Establishing New Fescue Stands
When planting a new fescue field, a
livestock producer should use seed known to have little or no (certainly
less than 5 percent) endophyte infection. In a few states, fescue seed
tags must state the percent endophyte infection. The importance of knowing
the level of endophyte infection in seed can hardly be overemphasized.
For example, when a beef producer uses endophyte-free seed, it can increase
returns by $75.00 or more per acre per year. This increased beef production
can be expected every year for the life of the stand!
New fescue plantings, even if endophyte-free,
should normally include a legume. Kentucky research indicates that clover
in an endophyte-free fescue stand will further increase young animal gains
by 0.2 pounds per animal per day. However, the primary justification for
planting a legume with fescue is that it can result in 2 or more years
of excellent animal performance with little or no nitrogen fertilizer expense.
White clover (preferably a Ladino type),
seeded at the rate of 2 to 4 pounds per acre, is the best clover companion
in most fescue pastures. However, red clover, at a rate of 10 to 15 pounds
per acre broadcast, or 8 pounds per acre drilled, is another good possibility,
especially when fields are to be cut for hay. Other legumes such as birdsfoot
trefoil or alfalfa may also be useful in certain situations.
It should be noted that interseeding
legumes at the same time endophyte-free fescue is seeded involves some
risk. Endophyte-free fescue seedlings may grow more slowly than endophyte-infected
fescue, therefore decreased competitive ability of the fescue may result.
For the same reason, it is not advisable to seed small grain, especially
ryegrass, at the same time endophyte-free fescue is being planted.
Dealing With Existing Endophyte-Infected Stands
Producers with established fescue fields
need to assess their situations carefully. Existing fescue stands should
be tested on a field-by-field basis. Several states now have laboratories
for determining endophyte level. County agricultural agents can provide
information regarding cost, sampling methods, and laboratory address(es).
Once the level of endophyte in existing
fescue pastures is known, a producer can select the best option for dealing
with the problem. The best way to handle one field may not be best for
another. Four general approaches are available:
effects on animals can be minimized with management practices. Grazing
and/or clipping management that keeps plants young and vegetative will
result in better animal performance. Likewise, if fescue is cut for hay
in the boot stage, better animal performance will be obtained than from
late-cut hay. Other practices such as chain harrowing, fertilizing, pest
control, creep grazing, and rotational grazing will result in improved
overall pasture quality and animal performance.
2. Avoid-the-Endophyte--Use of other
forage species avoids the endophyte. Using grasses other than infected
fescue for summer grazing will avoid the endophyte during the summer when
fescue forage quality is low. Since animal performance is adversely affected
by feeding infected fescue hay, feeding of hay of another species can also
3. Dilute-the-Endophyte--The endophyte
or its products can be diluted through the use of other feeds in the diet.
Growing legumes with infected fescue is an attractive option. Many studies
have shown increased pasture production, higher live-weight gains, and
improved pregnancy rates when pastures are renovated to include legumes.
4. Kill infected stands and replant--Low-endophyte
or endophyte-free seed is now readily available in most areas of the United
States where fescue is grown. Several excellent new varieties of fescue
have recently been released, and others are expected. Careful consideration
should be given to choosing low-endophyte seed. A new variety that is simply
"low-endophyte" or "endophyte-free" will be of little or no value if it
is not productive in the area in which it is to be grown. When selecting
a variety, attention should be given to adaptation, agronomic performance,
animal performance, persistence, and pest resistance. The best source of
variety information is university variety trials.
The cost of converting from high- to
low-endophyte fescue varies. Where fescue is used in rotation with other
crops, the only difference in cost will be the small price difference between
low- and high-endophyte seed. Where the sod is killed with a herbicide
and the seed drilled into the killed sod, the cost may be $30 to $50 per
acre. Where existing fescue is destroyed by tillage and immediately replanted,
the cost may be as high as $100 or more per acre.
Any infected fescue field which is
to be replanted should not be allowed to produce seed during the reestablishment
year. Seedhead formation should be prevented by heavy grazing, clipping,
or by chemical application. This is for the purpose of preventing the establishment
of volunteer infected plants.
Under usual storage conditions the
endophyte will die within one or two years. Thus, any volunteer plants
from old seed will usually be endophyte-free or have a very low level of
endophyte infection. Unfortunately, the germination level of fescue seed
may drop sharply during long-term storage, depending on temperature and
humidity conditions. Furthermore, the vigor of seedlings resulting from
planting old seed is likely to be reduced.
Methods of replacing endophyte-infected
A. Rotation--Rotating with other crops,
followed by seeding low-endophyte fescue, is an excellent approach. There
are many options ranging from no-till corn or a summer annual grass to
longer term rotations involving a perennial such as alfalfa or three annual
crops. With any rotation option, careful consideration must be given to
herbicide residues, erosion hazards (leave all waterways--it's better to
have a highly infected sod waterway than a non-infected gully), and the
complete destruction of the old fescue.
B. Prepared Seedbed - Certain situations
permit destroying the old sod through tillage, preparing a seedbed, and
then replanting non-infected fescue. However, it is often difficult to
completely destroy an old fescue sod by tillage.
C. Chemical Kill No-Till - Where methods
A and B are not feasible, chemical kill of infected stands followed by
no-tillage planting is the only remaining option. This technique can be
used to go directly from infected fescue 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 the existing infected fescue. In some
cases there may be common bermudagrass or other species which 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. Consult Extension Service recommendations on chemicals,
rates, and time of application.
Best results from no-till tests have
been found with late summer or early autumn seedings of fescue. Although
chemical kill has been satisfactory in spring, summer drought and competition
from warm season annual weeds tend to reduce stands of spring-seeded fescue.
A particularly effective approach 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 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. In this case, non-infected
fescue would be planted one year after the infected fescue was killed.
Use of annuals in this manner smothers fescue plants which escaped the
chemical treatment and also reduces the likelihood of insect damage to
seedling fescue plants.
Discovery of the fescue endophyte constitutes
a breakthrough of immense proportions. Most scientific advancements come
in small increments. In this case, we are seeing a dramatic increase in
the performance of animals grazing a tough, widely adapted perennial grass.
Despite some potential disadvantages, the proper establishment and management
of endophyte-free fescue constitutes an unprecedented opportunity for thousands
of livestock producers to obtain animal performance far superior to what
they would obtain by establishing, or keeping, endophyte-infected stands.
There are many endophyte-related studies
in progress, including several aimed at developing a better understanding
of fescue foot, fat necrosis, and horse reproductive problems. Future discoveries
may answer remaining questions relating to this problem and perhaps provide
additional solutions. It seems clear that application of the existing and
forthcoming technology relating to this breakthrough will have an immense
impact on livestock production in the fescue-growing region of the United
States, and perhaps in many other parts of the world.