|
|
Prevent
mycotoxin's harmful effects from impacting your horse's health
and performance.
Mycotoxins in Equine Feed
By
Trevor K. Smith, PhD, PAg
Mycotoxins
are harmful compounds produced by molds that live in the soil
but can grow on grains, forages and silages. They can develop
in the field pre-harvest and continue to form post harvest
if the feeds are stored in less-than-perfect conditions. In
addition, environmental conditions influence mold's lifecycle.
For example, high moisture content often predisposes feedstuffs
to mold growth and mycotoxin production. Likewise, temperature
is also an important influence - plants stressed by drought
and high temperatures are commonly invaded by mold spores,
and mycotoxins can result. Furthermore, recent global climate
changes have created climatic extremes, increasing the frequency
of mycotoxin contamination of cereal grains, forages and silages.
Effects of Mycotoxins
Mycotoxins can harm horse performance by altering both metabolism
and behavior. Metabolically, some mycotoxins damage liver,
kidney and reproductive tissues, and they can impair a horse's
immunity, making the animal more susceptible to infection
and disease challenges. Behaviorally, feed intake is the characteristic
most often harmed. Feeds contaminated with mycotoxins can
reduce a horse's feed intake, and without proper nutrition,
performance drops.
Types
of Mycotoxins
Although there are many varieties of mycotoxins, aflatoxin
and the various Fusarium mycotoxins have the greatest influence
on horse health.
|
|
Aflatoxin
Aflatoxin is produced by a tropical or semi-tropical mold
that thrives in high temperatures both in high humidity
and in drought conditions. Aflatoxin is one of the most
potently carcinogenic compounds known, which could be a
factor in the health of older equines. It targets the liver
causing weakened function and even death; chronic exposure
to even low doses of aflatoxin can result in liver cancer.
It also compromises the immune system increasing the chances
of infection and disease outbreak. Lastly, reduced feed
intake is yet another side effect of aflatoxin's presence.
Aflatoxin
content of animal feeds is regulated, but forages can also
be sources of it. This is much more difficult to monitor,
which complicates detecting aflatoxin traces. Since it thrives
in the heat, a drought can aggravate aflatoxin outbreaks.
For example, severe drought conditions in southern Europe
in 2003 resulted in significant aflatoxin contamination
of forages and silages. Similar drought conditions existed
across the mid-western United States in the 2005 crop year,
presenting western Iowa and eastern Illinois with high aflatoxin
contamination of corn crops - the first outbreak in many
years. Horse owners must be alert to the possibility of
aflatoxin contamination of equine feeds and monitor aflatoxin
residues when they detect poor performance.
Fusarium Mycotoxins
|
Historically equine leukoencephalomalcia,
also known as "moldy corn disease," was attributed
to mold-infested corn; however, ELEM can be caused by any
feed infected with Fusarium molds. |
| Fusarium
molds thrive in temperate climates and are common in the United
States. They can produce a wide variety of mycotoxins with
various effects on horses. One large group of compounds is
the trichothecenes. Although more than 100 trichothecenes
have been chemically identified, the most common is DON, also
know as deoxynivalenol or vomitoxin. DON and the other trichothecenes
affect horses in three ways. First, these compounds influence
behavior by reducing feed intake and weakening performance.
Secondly, they can cause bleeding and ulcers in the digestive
tract resulting in decreased nutrient absorption. Thirdly,
they suppress the immune system and increase susceptibility
to disease. Recent work by Raymond et al. (2003) showed that
feeding a concentrate containing a blend of grains naturally
contaminated with DON and other Fusarium mycotoxins resulted
in reduced feed intake and changes in blood chemistry indicative
of liver damage. When fed to mature, sedentary mares for 14
days in a different study, there was no significant effect
on body weight until the mares were exercised. Then weight
loss was visible (Raymond et al., 2005).
A second
important Fusarium mycotoxin is zearalenone. This compound's
estrogen-like properties upset normal hormone balance and
can cause infertility and abortions in horses and other
mammals.
The
fumonisins are another family of Fusarium mycotoxins. These
compounds affect the nervous system causing a host of neurological
signs such as muscle incoordination and ataxia. This can
result in equine leukoencephalomalcia (ELEM), a disease
specific to horses and characterized by a massive wasting
of brain tissues. In addition to this acute effect, the
fumonisins, like aflatoxin and the trichothecenes, suppress
the immune system.
Finding
a Solution
|
| To
completely avoid mycotoxin-induced side-effects, you must
avoid feeding mycotoxin-contaminated feedstuffs. Unfortunately,
mycotoxin-friendly climatic conditions are beyond our control;
therefore, even if feed grains can be monitored by strict
quality control, toxins escape notice in forages. Still, there
are methods to combat the toxins. One useful strategy is to
feed mycotoxin adsorbents. These non-nutritive feed additives
are not digested or fermented in the horse's digestive tract.
While passing through the digestive system, they can attract
and bind small molecules such as mycotoxins, preventing the
toxins from being absorbed into the blood stream. Therefore,
they cannot be carried to target tissues such as the brain,
reproductive tract and liver, which protects these tissues
from mycotoxin invasion. The mycotoxins are passed safely
in the manure, leaving internal organs free from harm. These
absorbents can be either inorganic or organic polymers. Inorganic
types are based on silica, generally referred to as clays;
organic molecules are carbon-based and are the equivalent
of plant fibers. In the publication of Raymond et al. (2003),
researchers showed that such an adsorbent extracted from the
cell wall of yeast was very effective in minimizing the effects
of DON and other Fusarium mycotoxins on feed intake and blood
chemistry. These results prove promising to preventing mycotoxin
damage through feed additives. |
Although mycotoxins are commonly associated
with moldy grains, forages can also be infected and are more
difficult to monitor. |
Although we know mycotoxins to be destructive, there isn't
enough research in horses to know the level where they become
harmful or toxic. Molds can exist virtually everywhere, so
their presence in feed is unavoidable - even if it is only
a trace. As a precaution, mycotoxin adsorbents are an effective
way to protect your horse from possible damaged performance
and health. They represent the most practical way to manage
mycotoxin challenges in the short term until longer term solutions
can be developed. |
|
Is
Your Feed Safe?
|
| Seminole
Feed has a two fold system to help protect your horse from
the potential dangers of mycotoxins. Firstly, Seminole Feed
employs strict quality control measures to ensure only the
safest quality grains are used when manufacturing the feeds.
In addition to visual, odor and moisture inspections, incoming
grains are tested using a screening test to detect traces
of the mycotoxins. If the grain does not meet our high standards
of quality assurance, the grain is not purchased.
Secondly,
a mycotoxin binder is added to our super premium feeds to
assist in protecting horses from mycotoxins that can be
present in forages. Mycotoxin binders are extracted from
the inner walls of yeast cells and binds mold-produced toxins
before they can be absorbed into the horse's bloodstream
and cause harm. A mycotoxin binder is found in the following
Seminole Feeds: Ultra Performance, Ultra Dynamix, Perfect
10, Perfect 12, Victory, Senior Formula, Mare & Foal,
Challenge, Equalizer and all Spillers/Seminole Feeds.
|
|
Trevor
K. Smith is a native of Vancouver, British Columbia, Canada
and completed
his PhD in Animal Nutrition at Cornell University. He is
a professor in the Dept. of Animal and Poultry Science at
the University of Guelph in Ontario, Canada.
|
 |
|
|
|
