TALL FESCUE/ENDOPHYTE/ANIMAL RELATIONSHIPS
Introduction
Tall fescue (Festuca arundinacea Schreb.) is a versatile
perennial grass used for livestock feed, various turf purposes and for
erosion control. Commonly referred to simply as "fescue," it is easy
to establish, tolerant of a wide range of management regimens and a good
forage yielder. Laboratory nutritive analyses of fescue compare favorably
to those of other cool-season grasses.
Fescue was first planted on a widespread basis in the USA in the
1940's, and now occupies some 35 million acres. Since the discovery
in the late 1970's that an endophyte (fungus) within this grass affects
both grazing animals and the grass itself, attitudes toward fescue have
changed greatly. This publication provides a review of current knowledge
of the effects of endophyte infected (EI), as compared to endophytefree
(EF) Fescue and explains options livestock producers have for using this
important grass.
LIVESTOCK DISORDERS
Fescue has numerous attributes, but three livestock disorders have come
to be associated with it. A brief description of these problems is
helpful in understanding the importance of fescue endophyte research.
Fescue Foot
"Fescue foot" is a dry, gangrenous condition of the extremities of the
bodies of cattle consuming fescue. Usually it causes lameness or
the loss of the tips of tails or ears, but may result in sloughing of hooves
or feet. Animal gains also are reduced. Fescue foot is generally
associated with cold weather.
Bovine Fat Necrosis
Bovine fat necrosis is characterized by the presence of masses of hard
fat in the abdominal cavities of cattle. This fat can cause digestive
or calving problems, but is likely to occur only where pastures are essentially
pure fescue and have been heavily fertilized with poultry liver or nitrogen
fertilizer.
Fescue Toxicity
The signs of fescue toxicity include: (1) reduced feed intake; (2) lower
weight gains: (3) decreased milk production; (4) higher respiration rates;
(5) elevated body temperature; (6) rough hair coats; (7) more time spent
in water and/or shade; (8) less time spent grazing; (9) excessive salivation;
(10) excessive blood serum prolactin levels; and (11) reduced reproductive
performance. Some or all of these responses have been observed with
dairy cattle, beef cattle and sheep consuming EI pasture, greenchop, hay
and/or seed. Fescue foot and bovine fat necrosis can be important to individual
producers, but are of relatively little consequence on a nationwide basis.
However, fescue toxicity is of widespread occurrence and of much economic
importance.
Horse Disorders
Reproductive difficulties of mares grazing fescue have been widely recognized.
They include: abortions, prolonged pregnancy, foaling problems which can
result in foal and/or mare deaths, thick or retained placentas and agalactia
(poor milk production).
ENDOPHYTE DISCOVERY
It is remarkable that a detrimental agent could have been undetected for
so long in such a widely grown forage species, but the fungal endophyte
Acremonium ceonophialum was not associated with animal disorders
until the title 1970's. Since then our understanding of the potentials
of fescue in livestock production has increased greatly.
Two characteristic, of the endophyte have real practical importance.
First, the fungus lives within fescue plants and does not affect the
appearance of the grass. A laboratory analysis is required to detect
its presence. Secondly, it is transmitted only by seed.
Thus, once an EF stand is established, it will remain non-infected unless
infected seed (either present before seeding EF Fescue or introduced later)
germinate and become established.
