Molds and Mycotoxins -
Feeding Mold and Mycotoxin Contaminated Wheat to Ruminants
Acceptable levels of normal uninfected wheat for
- lactating dairy cows, 15 - 20% of total ration dry matter (TRDM)
- lactating dairy cows, 25 - 40% of grain ration
- feedlot cattle, up to 40% of TRDM
- sheep, up to 40% of TRDM
The practical level of wheat in a ration depends on several factors
- the cost of wheat relative to other grains.
- the other grains being fed; in particular how rapidly their
starch breaks down in the rumen.
- the type and level of forage fed; in particular forage particle
- the feeding sequence, amounts fed per feeding or meal and bunk/manger
- the inclusion of buffers, sodium bicarbonate and/or magnesium
- the inclusion of an ionophore, Rumensin, Bovatec or Posistac.
- the inclusion of calcium carbonate.
- the mycotoxin levels in wheat will influence the acceptable
amount in a ration.
Agriculture and Agri-Food Canada guidelines for DON (Vomitoxin)
in animal feeds
- pigs, calves, lambs, lactating cows and lactating ewes, 1 ppm
in the diet.
- adult cattle, adult sheep and poultry, 5 ppm in the diet.
Initial corrective steps for Fusarium infected wheat
- clean moldy grains, remove fines and light weight grains suspected
of mycotoxin contamination.
- Reduce the energy levels of moldy wheat or light weight grains
by 5 - 10% and reformulate rations. Observe the limits on wheat.
- dilute mold or mycotoxin contaminated wheat with mold-free grains.
- if moderate effects on animals are noted, reduce the inclusion
of the suspected wheat by 50% of the amount in the ration.
- if effects on animals are severe, discontinue use of the wheat
for at least a week. If improvements are noted, sample the wheat
and have it retested to determine the safe level to feed.
Calculate the maximum inclusion levels of moldy wheat
- In the total ration dry matter safe level in TRDM level in wheat
DM x 100 = % maximum inclusion rate eg. for lactating cows - maximum
level DON is 1 ppm; if wheat analysis is 5 ppm DM then: 1 / 5
x 100 = 20% maximum inclusion level in TRDM based on DON level.
This does not exceed the nutritional limits listed above. Wheat
DON levels above 5 ppm will reduce the maximum inclusion level
below 20% wheat in TRDM.
- In grain rations for lactating cows, use the maximum grain level
fed not the average. The average ration may be 50% grain, but
early lactation cows may be up to 60% grain. eg. for lactating
cows - maximum level DON is 1 ppm; if wheat analysis is 5 ppm
a) 1 / 5 x 100 = 20% maximum inclusion level in TRDM.
b) 20% / 0.6 = 33% maximum wheat in the grain ration. This is
within the acceptable range given above.
- In feedlot cattle that tolerate a maximum of 5 ppm DON in the
TRDM, wheat DON levels above 12.5 ppm will reduce the maximum
inclusion level below 40% wheat in TRDM.
- Use the limits for the other toxins analyzed and follow the
same calculations as above to determine if they may be more limiting
to acceptable inclusion rates for wheat.
- Despite these calculations, poor palatability of moldy wheat
may lower feed intake. Palatability of the wheat may ultimately
determine acceptable inclusion rates. If in doubt, err on the
conservative side and watch for problems! Wheat must always be
introduced into the ration gradually.
Practical steps that may help
- Include aluminosilicate or bentonite in ruminant rations at
0.5% (or follow manufacturer's recommended rates) to reduce the
effects of mycotoxins. These compounds may bind mycotoxins in
the digestive tract and reduce their absorption. They are most
effective against aflatoxin and less effective on other mycotoxins.
- No products in Canada are registered yet by the Canadian Food
Inspection Agency to have a label claim for mitigating the effects
of toxins. You may wish to discuss additional options with your
nutritionist or veterinarian.
- In an attempt to alleviate the effects of mycotoxins, increase
the levels of Vitamins A, and E and trace minerals Selenium, Zinc,
Copper and Manganese. There are only anecdotal suggestions that
levels be increased by up to 25%. Note any overriding considerations;
eg. copper levels in sheep rations.
- Add an appropriate mold inhibitor (sodium or calcium propionate
or organic acids) to stored grain to prevent further development
- add 0.2 to 0.25% to non-ensiled feeds with 14 - 17% moisture
- add 0.5 to 0.6% to non-ensiled feeds with 18 - 24% moisture
(or follow the manufacturer's recommendations).
Watch these potential pitfalls
- Mycotoxins tend to be concentrated in the red dog, husk, light
grains, and broken kernels. Mycotoxins may be as much as five
times higher in the screenings compared to the grain. This may
be a year to be extra careful feeding "grain screenings".
- Mycotoxin contaminated wheat that may be used in the fermentation
industry poses a potential problem. The fermentation process does
not break down the mycotoxins. Mycotoxin concentration increases
in the distillers by-products. Check your source of distillers
grains for the type of grain used.
For more information:
Toll Free: 1-877-424-1300