Tall fescue is one of the most important cool-season
grasses in the US and has become a valuable grassland resource due to its
extended grazing season, pest resistance and tolerance to grazing pressure. But
the grassland source also has its shortcomings. Toxins produced by the
endophytic fungus grow symbiotically on tall fescue and have a wide range of
health implications for horses and pregnant mares.
"These toxins can reduce performance of horses by altering
both their metabolism and behaviour," Trevor Smith from the University of
Guelph said. "Reduced feed intake and subsequent reductions in performance
are commonly seen when feeds are contaminated with mycotoxins."
During his research of mycotoxins, Smith has worked on
finding a number of solutions to the exceeding problems of toxins in animal
One of the first steps Smith takes is examining materials for high
moisture. In this case, he suggests the use of a mold inhibitor. A mold
inhibitor can be applied to lower the pH so that molds will not grow and produce
more toxins. But as Smith noted, the product is only really useful if the
material is unstable and high moisture because it will only keep it from getting
worse by killing the mold spores.
enzymes are another approach to mycotoxins in feed. When a source of enzymes is
added to feed, the toxins are degraded and broken down in the intestinal tract;
they then do not enter the blood. While a number of enzymes are on the market,
Smith pointed out the problem with the enzyme approach is that it is most
suitable if there is only one toxin, such as alfatoxin because the enzymes are
The last strategy Smith advises
is the use of a suitable mycotoxin adsorbent. There are two types of adsorbents
-- silica-based polymers and carbon-based digestible fibers. Silica-type
materials are readily available and many have shown to be effective against
aflatoxins and also Fusarium toxins.
"The challenge with the clay materials
is that they are required to be in the feed at a very high level of inclusion,"
Smith said. "The advantage of the clay materials is the low price. If you put it
in at a high level, you lose the price advantage. If you don't put it in at a
high level, the silica clay materials tend to be
The other alternative is
carbon polymers or plant fibers. An example of one that Smith and other
researchers at University of Guelph found that worked well against Fusarium
toxins, including zearalenone and T2 toxins was the fiber from alfalfa. While
the fiber worked well, it too had to be added at a high inclusion level. Smith
said they also found that some of the fibrous plant materials like alfalfa can
be contaminated with Fusarium toxins as well.
"The only complete solution
to the problems arising from mycotoxins in equine feeds is to avoid the feeding
of mycotoxins-contaminated feedstuffs," Smith said. "But adverse climatic
conditions are, however, beyond our control so even if feed grains can be
monitored by strict quality control, forages cannot."
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