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NUTRITION – for Oct. 10, 2011

Last month we looked at the growing movement towards byproduct feeding. One of the best examples of this trend is the use of byproducts from the ethanol industry. The last 10 years has seen a dramatic expansion in the number of ethanol plants across North America. At last count there were over 200 producing plants in the United States and 16 in Canada.

A typical rule of thumb is that for every bushel of corn fermented, the distribution of co-products is approximately one-third ethanol, one-third feed byproduct (i. e. distillers grains) and one-third carbon dioxide. With approximately four billion bushels of corn used annually in the U.S., you can readily appreciate the huge volume of distillers grains available for feeding livestock.

There are several types of byproducts generated by ethanol plants. Their nature and nutritional value will vary depending on the nature of the plant. In a broad sense distillers byproducts can be classified by their moisture content. Wet distillers byproducts include wet distillers grains and distillers solubles (also known as thin stillage). Wet distillers grains have about the same moisture content as silage while thin stillage is greater than 90 per cent moisture. Obviously, to economically feed these products, you must be reasonably close to a plant. Some plants concentrate the thin stillage and market condensed distillers solubles at 20 to 40 per cent dry matter. This product is an excellent protein and energy source for cattle on poor-quality forage.

The most common feed byproduct from the ethanol industry is distillers dried grains with solubles or DDGS. This product is dry (90 per cent DM), has excellent shelf life and can be shipped anywhere in the world. Fed wet or dry it is an excellent source of protein, digestible fibre, fat and specific minerals. Since DDGS is the most commercially available of these byproducts, the remainder of this article will focus on its use.

One of the most surprising attributes of DDGS is its energy value. Numerous research and practical feeding results have shown that corn DDGS has a higher energy value than that of the original corn grain, typically 110 per cent or better. This combined with the fact that corn DDGS will average 30 per cent crude protein, gives you a feel for the value of this byproduct. In comparison, wheat DDGS will have a higher protein (36 to 40 per cent) but lower fat (four to six per cent) content. As a result the energy content of wheat DDGS is typically equal to that of barley grain.

While DDGS have traditionally been fed as a protein supplement, recently we are seeing a move to their use as an energy source in feedlot diets with 15 to 25 per cent of the grain replaced with either wheat or corn DDGS. At these levels, few issues with performance or carcass quality are reported. Some producers will even go to 40 per cent or more DDGS in the ration depending on the relative price of DDGS to barley or corn grain. However, at these inclusion rates, particularly with wheat DDGS, intakes will tend to increase while gains remain the same, thus negatively impacting feed efficiency.

In addition to its relative feed value, the fact that you do not have to process DDGS is another bonus. There are, however, some negative drawbacks to DDGS feeding. For example, outside storage can be an issue, particularly in windy locations. There is also the fact that when you include DDGS as a replacement for cereal grains at 20 to 40 per cent of a finishing ration (DM basis), in most cases you are overfeeding protein and certain minerals such as phosphorus and sulphur. Excess protein is excreted as urea in the urine while excess phosphorus ends up in the manure. While some may argue that this creates a more valuable fertilizer, we need to recognize the potential environmental consequences of overfeeding these nutrients. Urea can be hydrolyzed to ammonia and is lost to the atmosphere while excess phosphorus can lead to contamination of surface water bodies. A sound manure management plan that focuses on meeting plant nutrient requirements is a must if you are going to be feeding DDGS on a regular basis.

When feeding DDGS, it is also important to be aware of the sulphur intake of your cattle. High sulphur intake can lead to issues with polio as well as with cattle going off feed. The maximum sulphur content of the diet (DM basis) has been set by the National Research Council at 0.4 per cent. Since sulphur levels in DDGS can reach up to one per cent or greater, it is always a good idea to check with your feed company or nutritionist to ensure that you are not overfeeding this mineral.

Do byproducts have a future in your program? While the answer to this question is going to be dependent on where you reside and what byproducts are locally available, if you can do your homework on supply, pricing and nutrient content, for many of you byproduct feeding may well be the way to go.

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JohnMcKinnon isabeefcattle nutritionistat theUniversityof Saskatchewan

About the author


John McKinnon

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].



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