Feeding Co-Products of the Ethanol Industry to Beef Cattle

The US Energy Act, signed in December last year is going to see 15 billion gallons of ethanol produced from the corn sector alone. But the production of ethanol from corn will leave by-products that can still be used in feed for cattle, writes Chris Harris, Senior Editor, TheCattleSite.
calendar icon 4 April 2008
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The main part of corn that is used in ethanol production is the starch - which makes up 62 per cent of corn. Other constituents include 13 per cent water, nine per cent protein, 18 per cent fibre, four per cent fat and two per cent ash. At the recent National Cattlemen's Beef Association annual convention in Reno, Dr Greg Lardy of the Minnesota Corn Colleges said that the main interest for the ethanol manufacturers in corn is the starch, and the starch is removed through fermentation, which is a process requiring energy.

Dr Lardy said the dry milled corn, which can be food grade or used to produce alcohol as well as ethanol, produces, CO2 and then ethanol as it goes through the fermentation process. The remaining product is wet and dry distillers grain with solubles. During the fermentation process, a bushel of corn can produce between 2.7 and 2.8 gallons of ethanol, between 17 and 18 lbs of dried distiller grains with solubles or 54lbs of wet distiller grains with solubles and about 18 lbs of CO2. Some newer plants are aiming to make even more ethanol - up to three gallons per bushel, which will further reduce the nutrient content of the by products.


Source: NDSU Extension Service

Dried Distillers Grains Plus Solubles

Dr Lardy said that the residue DDGS has a variation in nutrient content with between 25 per cent and 32 per cent fat content and between 68 and 70NEg (Mcals per 100lbs) of energy. It also have between eight and 10 per cent fat content and trace elements of phosphorous (0.4-0.8 per cent), potassium (0.87-1.33 per cent) and sulphur (0.37-0.46 per cent). The protein content that was more than 60 per cent in the corn has now been reduced to just four per cent.

He said that the main concern is the sulphur content of the by-products, which is an additive in the form of sulphuric acid during the fermentation process. Excessive sulphur in the diet can cause polioencephalomalacia (PEM), which is a central nervous disorder. The maximum recommended sulphur level in dietary and water sources is 0.4 per cent.

"If the water has a high sulphate content then this could be raised by the sulphur being fed to cattle through the extra sulphur in the DGS," Dr Lardy said.

"DDGS are useful as a supplement to protein when they are added at a ration of between 10 per cent and 15 per cent," he added. "Feed at higher levels is an energy source."

However, Dr Lardy said that economics determine the correct level for feeding DDGS and a typical inclusion rate in the diet is between 15 per cent and 25 per cent.

The maximum recommended level is 40 per cent of the diet, but the higher the levels the higher the nitrogen and phosphorous content of the diet and also the sulphur content, which can cause problems.

Ration mixing is important in forage based diets and any separation of DDGS from forage is likely to increase any problems that could occur related to the presence of sulphur.

"You need moisture in the ration, so mixing is a key component," said Dr Lardy.

How DDGS is handled is equally important as the product does not pellet well because of the fat content and if it is pelleted needs to be mixed with wheat midds, soybean hulls or other by-products.

Dr Lardy added that DDGS also has several storage problems as the product has a tendency to "bridge" because of the texture of the product.

Wet Distillers Grains Plus Solubles

Wet Distillers Grains with solubles have a 65-75 per cent moisture content and 25-35 per cent dry matter and up to 35 per cent protein content on a dry matter basis and between eight and 12 per cent fat and up to 0.8 per cent phosphorous. The most common usage is in backgrounding and finishing rations including it in the diet at a rate of between 10 and 30 per cent, replacing a corn or protein supplement.

Dr Lardy said that now there the wet distillers grains with solubles are being modified to give a higher dry matter content of between 45-50 per cent. This new modified wet distillers grains with solubles is produced either by mixing WDGS with DDGS or by drying WDGS.

The inclusion rates in the diet are similar to those for WDGS.

However, Dr Lardy said there are added problems with storage with wet distillers grains with solubles, because it can freeze in the winter and it is susceptible to spoilage through mould.

"Some plants are now adding mould inhibitors to the product," Dr Lardy said.

Future for Distillers By-Products

Some bioenergy companies are now researching using corn to produce biodiesel and this will remove even more from the residue products. The production of biodiesel as well as ethanol with impinge on the fat content of the product, making the distillers grains highly rich in protein and fibre.

The removal of the fat content will also greatly reduce the energy content of the DGS.

In future as corn milling processes change the nutrient properties of the by products will alter through the different usages of the corn for ethanol and biodiesel.

However, Dr Lardy said that ethanol co-products will continue to increase and they are good sources of nutrients for beef cattle.

However, the farmer has to pay particular attention to the variability of the nutrient content and also pay attention to how the products are stored and transported to the farm and fed to the cattle.

In the long-run, however, the major question is about what effect feeding these by-products has on the quality of the meat. Dr Lardy said that research showed that there was no real effect on the shear force of the meat and taste tests reported no differences in flavour, tenderness and juiciness of the meat.

April 2008
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