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August 25, 2005 Test for DON Before Feeding Grain, Straw to Dairy Cattle North Dakota State University dairy cattle and veterinary experts are urging producers to test their crops for the mycotoxin DON before feeding the grain or forage to their livestock. Fusarium head blight, a plant disease also called scab, can produce DON, or deoxynivalenol. Scab is widespread in North Dakota and surrounding regions and in record high concentrations this summer. That means cash-crop producers are getting hammered on price at the elevator. "When grains are not fit for food or malting purposes, sellers often turn to livestock as an outlet," says J.W. Schroeder, NDSU Extension Service dairy specialist. "Unfortunately that is not always an acceptable alternative when it comes to dairy cattle, and your decision depends on the concentration of toxins and your ability to blend with uninfected grain." However, wheat and barley infected with DON still can be used as feed for beef cattle, according to Vern Anderson, an animal scientist at NDSU’s Carrington Research Extension Center. As a result of growing conditions in parts of North Dakota, scab has developed in many cereal crops, according to Michelle Mostrom, a research specialist at the North Dakota Veterinary Diagnostic Laboratory at NDSU. DON, also known as vomitoxin, has been found in straw as well. Because Fusarium mold typically infects the grain, experts have regarded baled straw from affected fields to be safe for most uses. But the high DON levels in some straw samples are cause for concern, Schroeder says. He and Mostrom recommend that if producers see scab in their cereal crops and plan on using the grain and/or straw in rations, they should consider consulting with their nutritionist or veterinarian and test the feed for vomitoxin. “Ruminants are fairly resistant to the clinical effects of vomitoxin, which can include such signs as decreased feed intake, milk production and weight gain, and a lowered immune response,” Mostrom says. “Dairy cows (and swine) will show effects at lower levels of vomitoxin in the ration when compared with beef cattle." As little as 1 part per million of DON can reduce daily weight gain in pigs significantly, especially those weighing less than 150 pounds. Higher concentrations result in feed refusal and vomiting. Nonbreeding cattle and poultry seem to tolerate both toxins. Research at NDSU indicates sheep and beef cattle both tolerate fairly high levels of DON. University of Manitoba researchers fed barley contaminated with DON levels of 8.4 parts per million (ppm) to midlactation Holstein cows. The diets had no significant effect on feed intake, milk yield, rumen pH (measure of acidity or alkalinity) or milk composition. But that was a controlled study, and producers’ results likely will vary, with other sources of natural infections possible from other grains in the diet, Schroeder notes. "Livestock producers must allow a margin of error in interpreting and applying test results,” he says. “Remember, the FDA (Food and Drug Administration) guidance level still is 2 ppm vomitoxin in the final ration of lactating dairy cattle." Anderson says that while producers can feed DON-infected wheat and barley to beef cattle, they should exercise normal care and bunk management. He suggests they coarse-roll the grains; feed them in diets mixed with other feeds and forages; add an ionophore supplement at rates their feed company recommends; and keep wheat at less than 50 percent of any concentrate portion of the diet. He also recommends they change the level of ingredients in rations slowly, over several days, and have feed available all the time or feed in multiple meals during the day. No data is available on feeding DON-infected grain to horses, so their owners should use caution when selecting feed for them, Anderson says. Every situation on the farm or ranch is different and should be handled on a case-by-case basis, Shroeder advises. He says that when producers are in doubt, they should test. Testing of grain, silage and straw is available from the North Dakota Veterinary Diagnostic Laboratory in Fargo. For more information, contact the lab at (701) 231-8307. The test for DON in cereal grain costs $25 for samples from North Dakota residents and $30 for out-of-state samples. Tests for zearalenone or other mycotoxins and for forage samples are $50 for in-state samples. "Because research on dairy cattle has been limited, there is no specific data on the effects of vomitoxin on reproduction," Schroeder says. "As a result, many dairy specialists recommend that vomitoxin-infected grain should not be fed during breeding and the first trimester of pregnancy. "Producers need to keep in mind that the toxicity of the feed containing vomitoxin may be increased when other mycotoxins, such as aflatoxin, zearalenone and other fusarium mold byproducts, are present," he says. "Also remember that sick animals or those with compromised immune systems are much more susceptible than healthy animals." ### Source:
J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu |
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