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At
this time of the year, as we prepare for the winter feeding season, I
receive several questions concerning feed toxins and other potential
problems that might be a hazard to your cattle. Animal feeds are subject
to contamination from different sources. More common during times of
drought, these toxins have the potential to harm your cattle and could
possibly cause death in extreme cases. The most common toxins we need to
be aware of in our area include, but not limited to, mycotoxins, acorn
toxicity, nitrates and prussic acid. Let’s look at each of these as a
potential hazard and determine ways to prevent them from being a problem
on your farm.
Mycotoxins
is the general term that includes aflatoxins, vomotoxin, and fumonsion
among others. These are types of fungi that have the capacity to impair
an animal’s health and productivity. Mycotoxin contamination of
forages and cereals frequently occurs in the field following infection
of plants with particular fungi or entophytes. Contamination may also
occur during processing and storage of harvested products and feed
whenever environmental conditions are appropriate for spoilage fungi.
The
mycotoxin we are most concerned with as a potential problem is aflatoxin.
Aflatoxins usually are found under conditions of high moisture/humidity
and temperature. Aflatoxin contamination of corn is a prevalent problem
in warm humid regions where the toxin may infect the crop prior to
harvest and remain viable during storage. Aflatoxin symptoms include
reduced feed intake, reduced reproductive performance, poor feed
efficiency and reduced susceptibility to stress. A test can be used to
determine the aflatoxin level in your product. Once a level has been
determined, you can decide the best way to feed the infected crop. If
you do have a high aflatoxin product, this may mean you only have to
blend the feed with other feeds to utilize it in animal feed.
Vomotoxin
is another mycotoxin that we need to be aware of in animal feeds.
Vomotoxin is very dangerous when fed at high levels. Horses are most
vunerable to vomotoxin with signs being brain necrosis and death. Other
clinical signs include abortions, uterine infections, nervous disorders,
hemorrhaging and vomiting. Vomotoxins are less likely to occur than
aflatoxins. These toxins can be found in grains and grain by-products. A
test can determine the level of vomotoxin in your grains with even low
levels causing concerns.
Fumonisin
is another mycotoxin that we can see problems from. This toxin can be
found in any of your grain products including oats, wheat, rye, barley
and corn. The biggest concern with this toxin is from a depressed immune
system. This will leave your animals more susceptible to disease and
sickness. In horses, this is a cause of Equine Leukoencephalomalacia or
deterioration of the brain.
While
mycotoxins will always be a concern in grains from high moisture, humid
regions of the country, we should also be concerned about the
possibility of toxins found in acorns. During periods of decreased
forage availability, cattle may seek out acorns as a food source.
Ingestion of too many acorns can lead to poisoning. Acorns contain a
substance called gallotannin. In the rumen, gallotannin is metabolized
to gallic and tannic acid. Tannic acid is very toxic to renal tubules,
and renal failure tends to be the hallmark of this disease. The toxins
in acorns seem to concentrate in milk; therefore, fast growing calves on
heavy milking cows will be the first to show signs. The most visible
signs of a possible acorn problem is constipation followed by a
decreased appetite. If cattle are removed from the acorns, most will
recover in a couple of days. Continued exposure will lead to black,
watery diarrhea; blood draining from the nose; severe depression;
straining to urinate and defecate; and death. There is no specific
antidote for this toxin. It is recommended to replace fluids and
electrolytes to keep the kidney operating, use broad spectrum
antibiotics to fight off infections, and use mineral oil as a laxative.
The most common practiced preventative is to supplement with calcium
hydroxide (hydrated lime) immediately before exposure has been effective
in mitigating signs of acorn toxicity. The most obvious prevention would
be to remove cattle from areas containing trees producing acorns.
Nitrate
toxicity is caused by the consumption of feed or water containing high
levels of nitrate nitrogen. Under most instances, forage plants will not
contain levels of nitrates high enough to be toxic. When this does
occur, it is a serious problem. The most common accumulation of nitrates
occurs in crops such as corn, millet, Bermuda grass, fescue, sorghum-sudan
and soybeans. Nitrates can also accumulate in weeds such as pigweed,
goldenrod and ragweeds. Nitrates are most often found in crops that were
heavily fertilized with nitrogen coinciding with the beginning of a
drought period. It is impossible to examine a sample of hay or silage
and determine the nitrate level. A laboratory analysis is required for
this. I would highly recommend that any producer who even suspects that
nitrates might be a problem to send off a sample for testing. The cost
is inexpensive and could save you thousands of dollars this winter.
Symptoms include labored breathing, muscle tremors and a staggering
gait, after which the cow falls down and dies quickly with little
struggle. The membranes of the eyes and mouth are bluish from a lack of
oxygen. The blood will be brown in color and turn red when exposed to
air. Nitrate toxicity usually results in death within a short period of
time, but can be prevented if you are alert to the problem. Medication
includes giving a 4 percent solution of Methylene Blue intravenously
using 100 cc per 1,000 pounds of body weight.
Prussic
acid is another potential toxin that producers should be aware of.
Prussic acid is usually found in large stem crops such as sudans and
millets. It is most often found in crops that are grazed right after a
frost in the fall. Symptoms include nervousness, reduced feed intake,
rapid body movements and death. The level of prussic acid will lower
over a ten to fourteen day period after the frost. It is also safe to
utilize hay that has been baled after a frost, as long enough time is
given for the acid levels to be reduced.
While
these are by no means the only toxins that we could see, they are the
most relevant in our area. As always if we can assist you in any manner
including collecting feed samples, sending them to laboratories and
discussing results, please contact your local Quality Co-op. I can also
be reached at jimmyh@alafarm.com.
Jimmy
Hughes is AFC’s animal nutritionist.
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