MORE ON FUMONISIN MYCOTOXICOSIS
It is always -interest-ing to get a thoughtful response to
something said, or written as in the FORUM. An executive
from a veterinary supply company takes me to task on my observation
that no cases of my-cotoxicosis due to fumonisinhave been
confirmed at the ADDL (Winter 1990 Diagnostic Forum) as he
feels (if 1 may paraphrase) that this may lead some producers
into a false sense of security.
His response in part states that "our company has been
providing feed/grain assay service to producers and we have
found a different story". The results of their assays
are listed as externalCFU (colony forming units of several
genera of fungi)/gm and internal infection rate of the kernels.
He goes on to say that this is not a toxin screen, but that
they have found a trend where high counts of mold spores and
internal infections of kernels generally result in problems
for the swine producer. No verification of this statement
was offered.
The innumeration of fungal spores and determination of internal
infection rates of kernels of corn is a valuable general indicator
of grain quality and may reflect poor nutritional value of
the grain. However, the presence of any number of fungal spores
cannot be construed as a direct measure of the presence of
toxic levels of any known mycotoxin. There are many more samples
of corn containing fungal spores than contain toxic levels
of mycotoxins.
As a veterinary lexicologist and diagnostician, I have a
more direct philosophical approach to diagnosing a myco-toxicosis.
A mycotoxicosis is a toxicologic disease caused by a mycotoxin;
mycotoxins are secondary metabolic products of certain fungi
(molds) that are sometimes produced, if climatic
and/or storage conditions are appropriate to allow them to
synthesize/make these mycotoxins. There is no question that
spores can be present and quan-titated in many lots/samples
of corn or other feeds.
But have they produced any one or variety of several well
known mycotoxins? I believe that the most direct method to
answer this question is to test for not only the presence
of specific mycotoxins, but also determine the concentrations/
levels. I mention levels because mycotoxins adhere to general
toxicologic principles, one of which is that they are dose
dependent. Therefore, a mycotoxin must be present at high
enough levels to cause a mycotoxicosis and produce a clinical
disease that is known to be associated with that specific
mycotoxin.
I believe that a valuable service could be provided to the
agricultural community if more commerciallaboratories offered
tests for specific mycotoxins, or screening tests for the
more common mycotoxins, in whole corn and other feeds. Many
diagnostic laboratories presently provide these tests. F.R.
Robinson, D.V.M., Ph.D. Veterinary Toxicologist
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