It was only about 20 years ago that investigation of an on-farm situation in Georgia, followed by a grazing experiment in Alabama, linked an endophyte (a fungus which grows inside plants) with the previously unexplained livestock disorder called fescue toxicity. Much information has since been generated about this endophyte and its effects, and the topic's importance justifies periodic reviews of key practical findings.

The Problems With Fescue

     At least three separate animal disorders are known to be related to the presence of the fescue endophyte.  These are commonly referred to as fescue foot, bovine fat necrosis, and fescue toxicity.  (Some may consider the unique impacts of the endophyte on horses to be a fourth type of disorder.)

     Bovine fat necrosis is associated with high levels of nitrogen fertilization.  It usually occurs in areas in which
heavy rates of poultry litter have been applied, and results in large deposits of fat within the abdominal cavity that cause complications in affected cattle.

     Fescue foot is a sloughing off of portions of the extremities of the bodies of livestock, including tails, tips of ears, and especially the rear feet.  It occurs most frequently in cool climates, probably because constriction of arteries is
caused both by cold weather (a defense against heat loss) and by fungus-produced toxins.  Thus, animals in cold climates are more likely to develop gangreen caused by severely reduced blood flow.

     Either bovine fat necrosis or fescue foot can be a serious problem for a producer, but the overall economic impact of fescue toxicity greatly eclipses that of the other two syndromes.  Etimates of the annual economic impact of fescue toxicity in the United States range as high as $1 billion.  Thus, most fescue endophyte research has focused on the fescue toxicity problem.

     The symptoms associated with fescue toxicity have been widely reported.  They include lower feed intake, lower weight gains, reduced milk production, higher respiration rates, higher body temperatures, rough hair coats, more time spent near (or in) water and/or in the shade, less time spent grazing, excessive salivation, and reduced reproductive performance.

     It is relatively easy to spot the rough hair coats and heat intolerance typical of fescue toxicity, but if one does not know what to look for, the problem may not be recognized.  Even in areas where fescue is commonly grown, there are certainly some (perhaps many) livestock producers who think these visual traits are normal, simply because they have seen them so frequently.

     The endophyte profoundly affects livestock weight gains.  For example, a summary of studies with steers (AL, AR, GA, KY, MO, OK, TN, TX, VA) revealed average daily gains (ADG's) of 1.61 vs 0.99 lbs on non-infected and infected fescue, respectively.  In studies with cows and calves (AL, KY, MS), ADG's for cows was 0.63 vs. -0.03 lb; for calves was 1.97 vs. 1.51 lb; and 205 day weaning weights for calves was 494 vs. 421 lbs, on non-infected and infected fescue, respectively.

     Though beef cattle have been the subject of most grazing and feeding trials pertaining to the endophyte, it is now known that other types of forage-consuming livestock are also adversely affected.  Furthermore, conception rates of livestock, including cattle, has in some cases been more than 40% lower on infected, than on non-infected, fescue.

     As compared to other livestock, endophyte impacts on horses are more difficult to detect visually, yet are of extreme importance.  Mares on infected fescue near the end of pregnancy are likely to have foaling problems, abort, or produce little or no milk.  Lower conception rates of horses grazing infected fescue may also occur.  Keeping mares off of infected fescue during the last three months of pregnancy is highly advisable.

Non-Infected Fescue Reaches The Farm

     After it was recognized that the endophyte causes livestock disorders, the exciting finding was made that the fungus spreads only through seed and that it does not move from plant to plant.  It appeared it would be a simple matter to kill existing infected stands, replant with non-infected seed, and by so doing make impressive and lasting increases in animal performance on fescue.

     Thus, when non-infected fescue became commercially available in the early 1980's, many producers purchased and planted it.  Unfortunately, it was soon learned both from experiments and producer experience that non-infected fescue is less stress-tolerant than infected.  Severe thinning of these newly-planted, non-infected stands was widespread, and many were ultimately lost, especially in hot climates prone to periodic droughts.

 Now that we have the benefit of over 15 years of research and producer experience relating to the fescue endophyte, our insights are far greater than they were initially.  We now better understand our options for eliminating or minimizing its impact,  and we recognize that there can be both problems and benefits  associated with exercising a particular option.

Dilution

     Research quickly revealed that when livestock consume other  forages or feeds along with infected fescue, the total amount of endophyte toxins consumed is lowered, thus reducing undesirable effects on animals.  Methods by which dilution can be accomplished include providing supplemental feed in addition to infected fescue pasture and/or hay, managing fields so as to encourage the growth of volunteer species along with fescue, and planting other forages into existing infected stands.

     For many producers, the most feasible means of dilution is to grow forage legumes with infected fescue.  In the Southeast, red clover, white clover, and annual lespedeza are most frequently used for this purpose.  Having even 10 to 20% of the ground cover comprised of legumes in a field otherwise dominated by infected fescue can substantially increase animal performance.

Avoidance

     In some cases, livestock producers can greatly reduce the impact of the endophyte by preventing certain types or classes of animals from having access to it.  The classic example is keeping brood mares off infected fescue during the latter stages of pregnancy, thus avoiding endophyte-related foaling problems.

     Avoidance can also be used with other livestock.  An example is that a dairy producer should not allow lactating animals to have access to infected fescue due to its highly detrimental effect on milk production, but grazing non-lactating animals should not cause a serious problem.  Likewise, a beef producer might allow cows but not yearlings to graze infected fescue.

     In some situations, it may be of benefit to exclude animals only during certain seasons.  Although the endophyte can lower animal gains at any time as compared to what they would be if no endophyte was present, it has a particularly adverse effect during warm weather.  Thus, if grazing of infected pastures is avoided only during warm weather, some benefit will occur.

Planting Endophyte-Free Fescue

     The decision as to whether to plant a new pasture with infected or non-infected seed is truly a dilemma for many
producers.  On the one hand, it is common knowledge that animal performance is much better on non-infected fescue.  However, informed producers are also aware that many people who have planted non-infected fescue have lost their stands, and thus confidence in non-infected fescue is low among many producers.

     It appears that two factors primarily affect the feasibility of planting non-infected fescue.  First, the climate needs to be sufficiently non-stressful to allow non-infected fescue to persist.  The hotter and/or dryer, and/or the more pest pressure (insects, diseases, competing plants, and nematodes) there will be, the less likely it is that non-infected fescue will survive.

     The second factor is level of management.  The way a field is managed also has a great influence on the amount of stress on the plants within it, so good management (particularly good grazing management) helps avoid stress.  Most agronomists recommend that non-infected fescue not be grazed or clipped closer than 3 or 4 inches, especially during the first year.

     Unfortunately, it is often difficult to determine in advance whether non-infected fescue will persist in a given area or even in a particular field.  Soil type and site have important influences, plus one cannot accurately predict what the weather will be in coming years, or what type of management the weather or other factors may force a producer to employ.

     In some cases, infected fescue has persisted even under poor management, especially in the cool and relatively non-stressful situations.  On the other hand, well-managed non-infected fescue has sometimes had severe stand losses due to climatic conditions.

     It may seem that no non-infected fescue is being grown successfully, but this is not the case.  Bad news travels faster than good news, so we tend to hear more about failures than about successes.  However, there are numerous producers using non-infected fescue successfully, even in our hot and humid climaate. A 1996 survey indicated that approximately ten percent of the fescue acreage in Alabama was non-infected.

     Should a producer plant infected or non-infected seed in a new field?  Without knowing specifics of a situation, the only statements which can be made are as follows.

     If climatic stresses will not be excessive and management will allow non-infected fescue to persist, then non-infected seed should be used.  In areas where the climate is highly stressful and/or management cannot (or will not) be exercised appropriately, infected fescue or some other forage species will be a better choice.

Converting Infected Fields to Non-Infected

     Converting existing infected fields to non-infected is more problematic than planting new fields to non-infected fescue.  The decision to re-establish is itself often difficult to make.

     On the one hand, who wants to grow a forage crop which is known to cause low performance and livestock disorders?  On the other, while infected fescue will not provide optimum animal performance, at least it is normally quite dependable.  In many areas that cannot be said for non-infected fescue.

     Once the decision has been made to convert a field from infected to non-infected fescue, more effort and care is required than when simply planting a new field to non-infected fescue.  The reason is that one has to be concerned both about killing the infected plants and also not allowing infected seed to germinate and contaminate the new non-infected stand.

     Often the most feasible way to convert from infected to non-infected fescue is to destroy the existing stand, then plant row crops for a couple of years.  This virtually assures the elimination of infected plants which may have escaped the initial attempt to kill the infected stand.  This is particularly important when tillage is relied upon to kill infected plants, as fescue can be difficult to kill with tillage alone.

     It is possible to successfully kill infected fescue and re-establish non-infected without using row crops and rotation, but it is more difficult, risky, expensive, and often inconvenient.  However, use of herbicides and/or tillage can in some cases quickly provide a thorough kill of infected plants, particularly if the existing infected fescue has been under prolonged stressed due to drought, heavy grazing, or other stress factors.

     Even in these cases, it is desirable to plant a "smother crop" such as a summer annual grass after killing infected fescue and before planting non-infected to make certain that most or all escapes are eliminated.  However, anytime tillage is used, it has the accompanying disadvantage of exposing the soil to erosion, which is a severe hazard in many pasture areas.

     When converting from infected to non-infected fescue, it is extremely important to prevent the infected fescue from making seed during the year of re-establishment.  This is to prevent volunteer infected plants from contaminating the new stand.  Seed in the soil which are more than one year old are normally not a concern in the Southeast, because after about a year the endophyte will normally die within seed.

     Non-infected plants do not become infected, but the percentage of infected plants in a mixed stand is likely to
increase over time.  This is because infected plants are more stress tolerant, they produce more seed, and a higher percentage of the seed are normally able to become established.  The higher the total stress level in a field, the greater is the likelihood (and the rate) of the shift toward a higher percentage of infected plants in mixed stands.

Animal Treatments or Supplements

      Many animal treatments, supplements, or additives have been investigated with regard to their potential for helping reduce the endophyte problem.  There have been reports of improved performance from using certain materials, but there has been no such material which which has been documented by independant research as constituting a clear-cut remedy for eliminating the impact of the endophyte on animal performance.

     Perhaps dewormers have resulted in the most encouraging results to date.  The effect of dewormers in this regard has not been highly consistent and is certainly not well-understood, but it seems clear that failure to control worms in yearling cattle grazing infected fescue is likely to result in extremely severe fescue toxicity.  The situation is unclear with mature animals.

Stocking Rate/Defoliation

     In contrast to the recommendation for non-infected fescue, keeping infected pastures grazed closely or at least clipping to eliminate seedheads has been found to be beneficial.  Livestock will selectively graze fescue seedheads even though they contain high levels of endophyte toxins.  Even where seedhead production is prevented, keeping infected fescue grazed closely improves animal gains because forage quality is better.

Management Of Non-Infected Stands

     Non-infected fescue requires a higher level of management than infected fescue.  As stated earlier, overgrazing is perhaps the worst mistake a producer can make with non-infected fescue.  Many producers are unable to provide good grazing management on all their pastures all of the time, so this may lead them to have one (or a few) non-infected fields while having others which are infected and which can be overgrazed if necessary.

     Livestock should not be moved directly from infected to non-infected fields because a small percentage of infected seed can pass through the bodies of animals and still remain capable of germinating and establishing infected plants.  To prevent contamination of a non-infected field, animals should be held in an area other than on infected fescue for about 72 hours prior to moving them to a non-infected field.

     Non-infected fescue stands tend to be thinner than infected fields.  This can be a benefit from the standpoint of the relative ease of establishing legumes with non-infected fescue, but may be a disadvantage from the standpoint of increasing the likelihood of invasion by unwanted species such as broadleaf weeds or common bermudagrass (which may or may not be unwanted).

Environmental Implications

     There has been little research work into the effects of the endophyte on wild animals.  However, the reproduction of animals commonly used in laboratory experiments (rats, rabbits, and mice) is severely upset by consumption of infected fescue forage.  We really can only speculate as to the effects on deer, birds, and other wild animals which may live in the vicinity of infected fescue fields, but they likely are significant.

     In addition, after the importance of the endophyte in tall fescue production and utilization was realized, scientists found that many other grasses (mostly wild grasses) also contain endophytes, though different than the one in fescue.  Because these endophytes have not been studied to any great extent, any roles they may have in animal performance or plant competitveness is largely unknown.

CONCLUSION

     There will undoubtedly be additional important developments pertaining to the fescue endophye situation in the
future.  These may include: (1) The development of more stress tolerant non-infected fescue varieties; (2) Development of a feed additive, antidote, or pharmaceutical product which will counteract endophyte toxins in livestock; or (3) The engineering or identification of strains of fescue endophyte which will allow excellent animal performance without causing disorders.

     Tall fescue has contributed greatly to livestock production in the past, but we now recognize that it may contribute much more in the future.  After 20 years of endophyte research much has been learned which is helping many producers reduce or eliminate problems with livestock grazing fescue.  However, we have not yet even come close to uncovering all the secrets associated with this fascinating area of study.