Every producer by now is
aware of die problems we been
experiencing with this year’s
com crop.
According to Penn State
agronomist Greg Roth, the cool
summer we had occurs only
once every 30 years. That
slowed the maturation of the
com plant, so that when the kill
ing frosts hit, a lot of moisture
was left in the kernels.
Grain dry-down this fall
averaged about 1 percent per
week, compared to 3.5 percent
per week in a normal year, Roth
says.
Those facts seem to be pretty
well understood, but producers
are still searching for solutions
amidst some messages that
seem a bit confusing. Since I
wrote on this subject in Decem
ber, we have a better handle on
how serious the problem is, and
it’s also apparent that some
laboratories are better than
others when it comes to myco
toxin analysis.
Time’s A-Wastin’!
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FEBRUARY 20 TO ASSURE
YOURSELF OF GETTING
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sake call us right now: 1-800-321-3177)
ATTENTION, Alert Corn Growers:
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and 5_ in Maryland. We have one near you.
Corn Mold
Update
by
Kenneth B. Kephart
Penn State Extension Swine Specialist
What Problems
Have We Seen?
Low test
weight grains
The cool conditions we had
this summer, or hot and dry
conditions lead to grains with a
low test weight (low bushel
weight) for grain.
While low test-weight grains
often have normal or higher
protein contents, they’re usual
ly lower in energy. If the drop in
energy density is not extreme,
low test weights will not
change growth rate, but feed
efficiency will be impaired;'
Data from Central Soya
Research shows that for each
pound decrease in bushel
weight, metabolizable energy
will drop by 5-10 kcal/pound.
For example, a 50-pound
bushel weight for com (vs. a
normal weight of 56 pounds)
would contain about 1,513
kcal/pound (vs. a normal ME
value of 1,555 kcal/pound).
Pigs consuming a diet with this
light-test com would grow 2-3
percent less efficiently.
Studies at Kansas State Uni
versity show pigs fed sorghum
with very low test weights
(35-45 pound vs. a normal of 55
pounds) will grow slower and
less efficiently. In those stu
dies, researchers observed a 5-7
percent reduction in growth
rate and a 7-12 percent reduc
tion in feed efficiency. These
observations fit the predictions
by the Central Soya Research.
When feeding suspect'
grains, check bushel weights
and protein contents. If these
two values are normal, hog per
formance should not change.
Damaged kernels
Com that contains more than
35-40 percent moisture may
break apart as it goes through
the harvesting and drying pro
cess. The fines that result are
open for mold infection, and
should not be fed to pigs. Fines
under normal conditions may
pose minimal risk even for pigs,
but this year they should be
unconditionally avoided.
Laboratory Tests
Blacklight
Some feed mills use a
“blacklight” as a screening
method for mold problems.
Shining an ultraviolet light
(wavelength of 365 nm) on a
sample of com will sometimes
cause kernels to glow bright
green-yellow. If one or more
kernels fluoresce in a 10-pound
sample, most mills will consid-
Corn Talk, Lancaster Farming, Saturday, February 13,1993—Page
(SflMKf fMJI WM§
PENNSYLVANIA MASTER CORN GROWERS ASSOC., INC.
er the sample positive for
aflatoxin.
Actually, the fluorescence is
due to compound, kojic acid,
that is produced by the Asper
gillus mold (which also pro
duces aflatoxin). Using the
blacklight alone will produce
both false positives and false
negatives.
Enzyme-linked
Immunosorbent Assay
This process, called ELISA,
is the concept behind the rapid
test kits that some producers
and many feed mills use. With
ELISA, an antibody in the kit
reacts with a specific
mycotoxin.
This reaction is often con
verted to a color change in the
solution, which tells the user
whether the sample is positive
or negative for the mycotoxin
in question.
The advantage is that the
ELISA test is quick. The disad
vantage is that the antibody in
the kit occasionally reacts with
something besides the mycoto
xin, which creates a false posi
tive reading.
Many researchers recom
mend that ELISA tests be fol
lowed with other procedures
wherein cross reactions are not
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replacement catalog...
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a problem. This is especially
true for dirty samples or pro
ducts of fermentation (silages).
This is simply a means of
separating and identifying a
mixture of compounds. You
will hear it by different names
thin layer chromatography
(TLC), gas liquid chromatogra
phy (GLC), or high pressure
liquid chromatography
(HPLC), to name a few. The
soup in question is introduced
at one end of the system (often a
“column” or lube), and the
components in the soup emerge
from the other end at different
times.
Chromatography is often
expensive, but as long as it’s
run properly, it’s more fool
proof than Elisa. It can be used
to accurately identify mycoto
xins (qualitative) and measure
the amount of mycotoxins
(quantitative).
Lab Test Results
From This
Year’s Crop
I recently spoke with Paul
Nelson, professor of plant
pathology and head of the
Fusarium Research Center at
1-800-321-3177
Chromatography
(Turn to Page 26)
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