Perspectives - Spring 2018 - 32

AGRONOMIC PRACTICES
INFLUENCE MYCOTOXIN
CONTAMINATION IN FEEDS
BY PAIGE GOTT, PHD,
RUMINANT TECHNICAL MANAGER,
BIOMIN AMERICA INC.

T

he risk of mycotoxin contamination in
feeds falls somewhere between "things
you can change" and "things you cannot
change." The wisdom comes in knowing
ways to limit the risk, but also understanding that mycotoxin challenges may exist
despite your best prevention efforts. A
comprehensive mycotoxin risk management program is essential from the field to
feeding out. This article will discuss agronomic factors that play a role in the development of fungal disease and subsequent
mycotoxin production, but first, some basic
mycotoxin information will be reviewed.
Mycotoxin Basics
Mycotoxins are toxic secondary metabolites produced by molds. That means that
mycotoxins are not required for the mold
to grow, survive, or reproduce, but it is
thought these metabolites might provide a
competitive advantage to the mold or protect the mold from parasites, and they may
serve other unknown purposes. More than
400 mycotoxins are known to exist, but
relatively few have been studied and are
well-understood when it comes to their potential negative effects in cattle. The most
studied mycotoxins, which are frequently
detected and likely to cause harm, are often
grouped into six major categories including: aflatoxins, trichothecenes (including
deoxynivalenol (DON which is commonly
referred to as "vomitoxin" as well as T-2
toxin), fumonisins (FUM), zearalenone
(ZEN), ochratoxins, and ergot alkaloids.
Although additional mycotoxins frequently occur, more research is needed to better
understand what risk many of them pose
to cattle.
Many molds are able to contaminate
feeds, but relatively few types are known
to produce metabolites which are harmful
to animals. The Fusarium species of molds

32

Perspectives Magazine

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are associated with growth and mycotoxin
production (including DON, ZEN, FUM
and T-2) in the field while Aspergillus and
Penicillium species (aflatoxins and ochratoxins) are categorized as storage fungi.
Exceptions can occur which enable storage fungi to contaminate crops in the field
and field fungi may continue to produce
mycotoxins post-harvest if proper storage
practices are not upheld. Although visible
mold growth on feed does not guarantee
the presence of mycotoxins, mold does indicate increased risk for contamination and
can also reduce feed quality and palatability even if toxins do not exist. Additionally, mycotoxins are more stable than the
molds that produce them, so the mold can
die and may no longer be present, but the
mycotoxins will persist. Therefore, visual
inspection of feed alone cannot positively
identify whether mycotoxins are present or
not.
An array of feed ingredients, including
grains, forages, their byproducts, and other feedstuffs such as fruits and nuts, can
be contaminated with mycotoxins. Dairy
rations are complex, and are often formulated with the aforementioned ingredients,
thus providing multiple potential sources
of contamination. Consumption of feed
contaminated with multiple mycotoxins
can lead to synergistic-not just additive-
effects. This means the presence of more
than one toxin may intensify the negative
effect(s) of the other mycotoxins present,
resulting in even poorer performance than
would be expected from the individual
toxins alone. Many of these combinations
and relationships are not fully understood,
but it is common to see animal health and
performance impacted in the field at toxin concentrations well below the tolerance
levels described in research studies.
Mycotoxins result in a variety of negative

effects when ingested. Some toxins target
and damage specific organs such as the liver or kidneys. In general, many mycotoxins
can cause immune dysfunction, resulting in
an increased risk of disease. Multiple factors including the specific mycotoxin, level
and duration of exposure, animal species,
age of the animal, and animal health status
as well as environmental factors and other
stressors play a role in how the animal will
be impacted by mycotoxins. High levels of
mycotoxins are generally needed for the
expression of classical signs of mycotoxicosis, but low to moderate levels can cause
problems that are less easily identified, but
still reduce animal performance and health.
Complex Nature of Mycotoxins
Implementation of best management
practices-at planting and during harvest
and storage-can help reduce the risk of
mold infection and subsequent mycotoxin
production, but some factors influencing
those events are beyond control (such as
the weather). Additionally, limitations exist in different production systems and areas as to what agronomic practices may be
used.
Both the molds that produce mycotoxins
and the plants they infect are living organisms that can adapt and adjust to challenges over time. Many factors influence
mold growth and mycotoxin formation,
including temperature, moisture content,
oxygen levels, and physical damage to the
crop. Stress factors, including drought or
excessive rainfall, can increase plant susceptibility to mold colonization and mycotoxin formation. Due to the many "moving
parts" involved in the development of mycotoxins, complete prevention of contamination is difficult, especially since mycotoxins can be produced while the plant is
in the field or once the feed is in storage.


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