Mycotoxins in Swine Diets
Wednesday, November 17, 2010
Prairie Swine Research Centre warns pig producers about the dangers of feeding mycotoxin-contaminated cereals to pigs. Levels of DON and zearalenone are high in this year's crops as the weather conditions have favoured the growth of the fusarium fungus.
Why it is Important Now
The cool, wet weather experienced in Canada this summer has caused many problems for the farmers in this area. This fall there is one more – there are reports of grain that is contaminated with fusarium mould.
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Deoxynivalenol (a.k.a. DON, vomitoxin) is a mycotoxin that can be produced when fusarium moulds contaminate cereal grains, including wheat, barley and corn. Pigs are more sensitive to DON contamination in their feed than other farm animals. Growing beef cattle, sheep and poultry have an Agriculture Canada Guideline of 5 ppm, while the guideline for pigs is 1ppm (1mg/kg) .
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The most common symptom pigs show when given DON-contaminated feed is a reduction of feed intake and a corresponding decrease in weight gain. Some decrease in feed intake will likely be seen if DON contamination exceeds 1ppm.
In research conducted at the Prairie Swine Centre, feed intake and daily gain of late nursery pigs decreased 9.1 and 5.2 per cent, respectively, when pigs were fed diets containing 1.57 ppm DON for 22 days. Although pigs may vomit at high levels of DON contamination (above 20 ppm), it is more likely that they will refuse feed completely (around 12 ppm) before that occurs. Younger animals will be more severely affected than older animals. While the general recommendation for swine is to limit DON in diets for pigs to less than 1ppm, a maximum of 0.50ppm is preferable for nursery pigs.
While there does not seem to be direct negative reproductive effects from feeding DON contaminated diets to breeding stock, the reduced feed intake itself may be a problem. Therefore, DON-contaminated feeds should be avoided in diets for breeding stock whenever possible.
Cross-Contamination
Often when feed is contaminated with one type of mycotoxin another type will also be present. For example, feed contaminated with DON can also be contaminated with zearalenone, another mycotoxin caused by fusarium.
As with DON, zearalenone affects pigs more than other farm animals. Zearalenone has oestrogenic effects and when present in the feed, it causes vulva enlargement in pre-pubescent gilts, as well as decreased litter size and infertility. Keep zearalenone concentrations under 0.5ppm for all swine and avoid using zearalenone-contaminated grains altogether in diets for breeding and replacement swine.
Sampling
It is difficult to get a good sample of grain to test for mycotoxin contamination. There is usually a great deal of variation in the amount of mycotoxin present from one area to another within a truck or bin. Therefore, it is easy to get false negatives or lower or higher values than are actually present in the overall grain. Combining small samples from several different areas will help you be sure that a representative sample has been obtained.
The following (Table 1) is an example of our sampling data from 10 different one-tonne totes of corn obtained from a single source. The differences between labs may be partially explained by differences in procedures and timing of analysis.
What to do
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There are no feed additives approved in Canada to decrease the impact of DON on swine. Cleaning grain to decrease dust and small shrivelled kernels helps lower the concentration of DON in the grain. If possible, feed contaminated grains to less sensitive species and use clean grains in swine diets.
Fast Facts
- Mould produces mycotoxins but high mould content does not mean mycotoxins are present and mycotoxins can be present when there is no longer any mould.
- Not all moulds produce mycotoxins.
- Swine are the farm animal most sensitive to DON (also known as deoxynivalenol, vomitoxin).
- Limit DON to less than 1ppm in diets for swine.
References:
van Heugten, E., 2000. Mycotoxins and other antinutritional factors in swine feeds. In: Swine Nutrition. A. J. Lewis, L. L. Southern, ed. CRC Press, Boca Raton, FL, p563–583.
Dupchak, K. Feeding Fusarium-Contaminated Grain to Livestock. University of Manitoba. accessed 29/09/2010.
CAST. 2003. Mycotoxins – risks in plants, animal, and humans. Ames, Iowa, USA.
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