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Distillers grains have health risksBy Arden
Wohlers DVM Dried distillers grains and corn gluten feed have become the buzz words to the beef industry. As ethanol plants continue to be built, the by-products from them become more readily available. Extensive research at university feed yards have proven the nutritional and economic value of these by-products to the beef industry in Nebraska. Most research has centered on animals in the finishing phase of their life. But we are seeing increasing amounts of the products being fed on ranches to background calves as well as the beef cow herd. Unfortunately with any product, there are always negatives along with the positives. During the ethanol distillation process certain elements in the by-products used as animal feed have a chance of accumulating to levels that could be toxic to the animals. The process that is used to extract starch leaves residual sulfur. At low levels sulfur plays an important role in protein, fat, carbohydrate and energy metabolism. However the process can leave four times the sulfur concentration in ethanol by-products as the sulfur content of corn silage. Higher sulfur levels can reduce copper absorption in animals and result in signs of copper deficiency. Severe copper deficiency can result in signs as pronounced as death, but is more often sub clinically evident as decreased immune function and subpar fertility in the beef cow herd. At the feed yard there is concern because it appears that sulfur can destroy thiamine in the rumen. Thiamine deficiency creates polioencephalomalacia (brainers), a softening of the brain in cattle. It is important to determine the total sulfur levels of all feed and the water source when feeding by-products to cattle for proper nutrient balancing of the ration. The ration should be balanced with a maximum of 0.4% total sulfur on a dry matter basis. The high sulfur levels may possibly be neutralized by adding more copper in chelated form or thiamine to the diet. Corn by-products have also concentrated phosphorus to four times the level that is present in corn silage. This can be a cost-saver, as phosphorus is an expensive component of your mineral mix. Sometimes calcium will need to be added to keep the calcium:phosporus ratio between 1 and 2:1. If this ratio isn’t met there can be increased risk of urinary calculi in steers. This high phosphorus does pass through in the manure and may create problems for feed yards in manure disposal. Feed yards may need more land for proper manure disposal as phosphorus binds to the soil and concentrations are slow to decrease. The ranch situation is different because cow to land density is low enough that phosphorus levels will not be a problem. A remaining concern is the formation of mycotoxins by fungi that will grow on corn during years that climatic conditions are favorable. Mycotoxins in corn occur more frequently in regions that have high temperatures and high humidity. They can reach dangerous levels in particular if there is drought stress at the time of pollination. Corn that has not been stored properly has a greater chance of having mycotoxins. Aflatoxin is a mycotoxin that is one of the most toxic naturally occurring compounds known to man. Aflatoxin can be concentrated four-fold in dried distillers grains over that contained in the contaminated corn. Consumption of aflatoxins can lead to death within 72 hours, but it is more common to result in reduced growth rate, impaired fertility and mild diarrhea. When distillers grains are used as the protein supplement for range cows, composing less than 20% of the ration, any aflatoxin present would usually be diluted to safe levels. Cows that are placed in a dry lot and fed higher levels of distillers grains would cause more concerns. Some years large quantities of corn have higher levels of aflatoxins than other years. In those years if feed is composed of high levels of distillers grains it should be tested for aflatoxin content. The by-products of corn milling are becoming more readily available and are finding their way into range cow supplements as well as in the feed yard rations. They can be safely fed if the total ration is balanced for minerals as well as for protein and energy. Some sources of the by-products should be tested for mycotoxins.
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