DON: How much is too much?

Based on this year’s weather conditions throughout parts of the U.S. and Canada, the threat of deoxynivalenol (commonly referred to as vomitoxin or DON) in wheat crop is a real issue farmers are currently facing. But when it comes to knowing how much DON-contaminated wheat grain or wheat straw farmers can actually feed animals without incurring negative production and health effects, the questions of how much is too much comes top of mind.

An article recently published by Agri-View, discusses this conundrum and suggests that before feeding any potentially contaminated wheat grain or wheat straw, farmers should sample the product to determine its contamination level. Once you know the contamination level, you can then determine how much you can feed before you reach the upper DON limit.

Swine are most susceptible to this toxin and current recommendations suggest an up
per limit of 1 part per million(ppm) of the total diet dry matter. Dairy cattle are less susceptible than swine and current guidelines suggest an upper limit of 5 ppm in the total diet dry matter; however, some recommendations suggest the upper limit should be in the 2-to 3-ppm range.

In addition, if wheat grains have tested high for DON contamination, wheat straw will probably also have if the same high results. This is important because wheat straw is commonly fed at relatively high levels in dry cow and fresh cow diets.

The article lays out the following examples:

Example 1: You decide to feed 3.5 pounds of dry matter from wheat and you know the DON level is 10 ppm. This means that 6.6% of the diet dry matter is from wheat (3.5 pounds wheat / 53 pounds dry matter intake (DMI)).Multiply that by 10 ppm and you find a 0.66-ppm contribution of DON from wheat. The total diet should be less than 5ppm DON.

Example 2:  You determine that you have 8 ppm of DON in the straw and you are feeding 6 pounds of straw diet dry matter. The straw would contribute 1.70 ppm of DON to the total diet ((6 pounds / 28 pounds DMI) x 8 ppm = 1.7 ppm).

When you compare these results to the corresponding dietary thresholds, you can easily tell what amount are safe. However, the article states it is still very important to work closely with your nutritionist to make sure you are not reaching the DON threshold in your diets.

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