Mold & Mycotoxins
UW-Extension Swine Team
The 2009 growing season has provided farmers with many concerns. At first it was the high input costs, and then a cool growing season stressed crops. A very wet October delayed corn maturity and resulted in a wet corn crop with high moisture content and mold growth on the standing crop. This wet fall, and a heavy snowfall has left 10-20% of the corn remaining in the field with much concern about mold and mycotoxins in the harvested grain. Feed corn with molds or mycotoxins in the 2009 crop is now the issue. An ear mold survey conducted by Paul Esker, Field Crop Extension Plant Pathologist, included 84 samples of corn from 31 counties. This survey revealed almost all samples contained Fusarium spp. and Cladosporium but no Aspergillus. Because of these finding we will concentrate on deoxynivalenol (DON or vomitoxin) zearalenone, T-2 toxin and fumonison mycotoxins.
What are molds and mycotoxins?
Molds are fungi that grow on grain and feed that may reduce feed value by up to 10%. Some signs of mold in feed are: dustiness, caking, poor feed flow in bins and feeder, feed refusal, a musty smell and change of feed color. Mycotoxins are the highly toxic by-product of mold grown in the grain. Mycotoxins are poisons that can cause serious problems in livestock including reduced feed consumption, poor feed conversion, reduced immune function and reproductive problems in breeding stock. Mycotoxins come in with the grain from the field and can be reduced by cleaning the fines and cracked kernels, but mycotoxins are not destroyed by the drying process.
Signs and symptoms of mycotoxins being present in your feed.
Vomitoxin (DON) in feed is produced by Fusarium spp and producers may notice feed refusal or vomiting, diarrhea, reduced growth and increased disease as animals are under stress. Zearalenone mycotoxins are a group of estrogenic metabolites that cause reproductive problems that are shown by swollen vulvas, false pregnancies and silent estrus. Sows may breed but not get pregnant. Growing and finishing pigs may have reduced growth, and poor feed efficiency. T-2 toxins are more associated with digestive disorders, bloody diarrhea, and hemorrhaging lesions of internal organs. If you notice any of these signs or are aware of high mold counts at harvest a 2 pound sample of corn or feed should be tested.
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Where to send the samples.
Although there are several labs that can analyze for mycotoxins here are a few in Wisconsin.
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Rock River Laboratory, Inc
710 Commerce Drive
PO Box 169
Watertown, WI 53094 -0169
920-261-0446
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Agsource Soil and Forage Laboratory
106 North Cecil Street
Bonduel, WI 54107
715-758-2178
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Convance Laboratories
3305 Kinsman Boulevard
Madison, WI 53707
608-241-4471
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Dairyland Laboratories
217 east Main Street
Arcadia, WI 54612
608-323-2123
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The chart below shows levels of mycotoxins to stay under for best performance.
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Mycotoxin Levels In Swine Diets
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Deoxynivalenol (DON)
ppm
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Zearalenone
ppm
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Breeding Herd
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1.0
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2.0
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Young
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1.0
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1.0
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Growing
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1.0
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1.0
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Finishing
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1.0
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3.0
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Young Males
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1.0
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3.0
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Old Males
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1.0
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3.0
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Ref: 57th Minnesota Nutrition Conference Proceedings: Sept.,1996:
J.D. Hawton: University of Minnesota: pages 269-294
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Possible solutions
High levels of mycotoxins are sometimes very troublesome to manage. Here is a list of possible solutions to help on your farm.
1. Clean all feeders and only grind for 10-14 day supply in feeder. To reduce second mold growth in warmer buildings and be able to change feeds if problems arise.
2. Clean fines and smaller kernels out of corn. Best if done on the way into the bin but could do on way to grinder if needed.
3. Dry and aerate grain in bin to reduce moisture migration. Grain should be cooled in the fall and warmed in the spring. Make sure to check bins on a regular basis.
4. Sell poor mycotoxin corn first and feed best corn.
5. Dilute mycotoxin corn with last year’s corn or with non mycotoxin corn if levels are not too high.
6. If you have cattle, feed mycotoxin corn to steers as they can tolerate higher levels than swine. Check levels for ruminate animals.
7. Feed binder that is developed specifically for your mycotoxin. You may need to raise vitamin levels (specifically Vitamin B complex, Thiamin and Niacin) and reformulate as the binder may reduce feed utilization as well. Increased Lysine levels may help. Your nutritionist should be able to recommend appropriate changes.