Molds and Mycotoxins - Feeding mold and mycotoxin contaminated wheat to swine
Contamination in wheat can result in substantial quantities being available as livestock feed. As a general rule, if wheat costs the same or less than corn, then it is a good buy.
Guidelines for feeding mycotoxin-infected wheat
The optimum solution is to buy clean grain for swine and feed the contaminated grain to cattle. Feeder cattle should be able to safely consume levels five to 10 times higher than swine. If contaminated wheat must be fed, the following table lists maximum levels in swine diets for vomitoxin and zearalenone.
|Age Group||Vomitoxin (DON), ppm||
* These levels should be adjusted downward if feed intake is reduced or other obvious signs of toxicity are observed.*Source: Kansas Swine Nutrition Guide
Acceptable levels of normal uninfected wheat for swine
- starter/grower/finisher, up to 100% of grain portion of ration
- gestating/lactating sows, up to 50% of ration
The practical level of wheat in a ration depends on several factors
- the economics.
- when wheat is used in pig feeds, close attention to feed processing and fineness of grind is essential to avoid problems with palatability, bridging in feeders and incidence of stomach ulcers.
- the mycotoxin levels in wheat will influence the acceptable amount in a ration.
Initial corrective steps for Fusarium infected wheat
- clean moldy grains, remove fines and light weight grains suspected of mycotoxin contamination.
- 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.
Sampling method for dry feeds (Penn State University)
- Take 8 - 12 samples at each of 3 - 5 feedings or feed removal from storage or take 12 - 20 stream samples from an entire delivery, or 12 - 20 deep probe samples from a bin. Include samples from the sides of bins or edges of storage where mold is likely to occur.
- Mix the subsamples well, take a 500 g composite sample for submission to the laboratory. Some labs recommend taking a composite sample of 1 kg for mycotoxin analysis.
- Keep an additional 500g sample for confirmation or other analyses.
- Store all samples in clean double layer paper (grocery store) or cotton bags.
- Store in a cool dry place. Submit to the lab as soon as possible.
- Always check the basis on which results are given - often they
are on an as-fed basis. Correct these to a dry matter basis so
that inclusion rates can be calculated.
eg. Wheat with 15% moisture analyzed at 5 ppm DON as-fed.
100 - 15 = 85% dry matter
5 / 0.85 = 5.9 ppm DON on a dry matter basis.
- Results may be expressed in a number of different ways.
ppm = mg/kg = ug/g = 1,000 ppb
Calculate the maximum inclusion level of moldy wheat
- In the total ration dry matter (TRDM) safe level in TRDM level in wheat DM x 100 = % maximum inclusion rate eg. for lactating sows, 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.
- Use the limits for the other toxins analyzed and repeat 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
- if mild contamination is suspected, increase the nutrient levels of the ration to help compensate for the reduced intake.
- increase the levels of vitamins, minerals, and amino acids by 5-20% depending on severity of feed refusal.
- add an appropriate mold inhibitor (sodium or calcium propionate or organic acids) to stored grain to prevent further development of molds.
Watch these potential pitfalls
- Mycotoxins tend to be concentrated in the hulls or outer covering of grains. As a result, mycotoxins may be as much as five times higher in grain by-products, such as wheat midds, "screenings", etc. This may be a year to be extra careful feeding these types of by-products.
- Gestating sows on limit fed rations may consume large quantities of mycotoxin-contaminated straw, resulting in toxicity. However, this should not be a problem for finishing pigs that have access to clean feed.
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