Ethanol By-Products - a Good Feed Additive08 February 2008
By Chris Harris, Senior Editor, TheCattleSite. Ethanol co-products are good sources of nutrients for beef cattle and their availability is going to grow as more and more corn is being devoted to the production of the biofuel.
Speaking at the National Cattlemen's Beef Association annual convention in Reno Nevada, Dr Greg Lardy for the University of Minnesota Corn Colleges said that Dried Distillers Grains plus Solubles - DDGS - are an important addition to cattle feed.
The corn ethanol industry takes the starch out of the corn during distillation. This accounts for more than 60 per cent of the composition of the corn. The rest of the corn is nine per cent protein, 13 per cent water, 18 per cent fibre, four per cent fat and two per cent ash. These remaining constituents form the DDGS for the feed.
However, Dr Lardy said that the production of ethanol through fermentation also requires an input of energy to heat the process and it also produces carbon dioxide.
One bushel of corn produces between 2.7 and 2.8 gallons of ethanol and between 17 and 28 pounds of DDGS and 18 pounds of CO2. Newer plants are claiming to be able to produce even more ethanol.
By removing the starch from the corn, the resulting feed is rich in protein and fat and it also has trace elements of phosphorous and sulphur.
"The sulphur content is a concern," said Dr Lardy.
"It is added during the fermentation process, through the addition of sulphuric acid to improve fermentation."
The DDGS contains about 25-32 per cent protein, eight to 10 per cent fat 0.4-0.8 per cent phosphorous, 0.87-1.33 per cent potassium and 0.37 to 0.46 per cent sulphur as well as 60 to 70 NEg (Mcals/100lbs of energy).
"DDGS are a useful as a supplement," Dr Lardy said.
However, the proportions at which they should be used have to be carefully controlled.
He said that if they are fed at a ratio of 10 per cent to the natural feed, they become a rich source of protein. If they are fed at higher ratios, then they become an energy source for the animal.
However, he warned that too much addition to the diet will mean that the cattle are being "fed well in excess of what is required."
Dr Lardy said that the inclusion limitations should be about 15 per cent DDGS in a dry mix and slightly higher if the product is wet.
One of the disadvantages in DDGS is that it does not pellet well because of the high fat content and there are also problems with storage because of the consistency of the product. He said the moisture in the product tends to make it "bridge" in storage - stick together and form peaks in then piles as it is stored.
He added that storage problems also arise even when the product is covered because of a tendency for it to form mould on the surface. It also suffers from severe temperature changes that are experienced in some parts of the US.
He said that ration mixing is key in forage based diets and that separation of DDGS from forages starts to increase the likelihood of sulphur related problems.
One of the most severe problems that can be caused through the sulphur content of the DDGS mixes is Polioencephalomalacia. This occurs because excess sulphur results in the production of hydrogen sulphide which interferes with cellular energy production.
The maximum recommended sulphur level is 0.4 per cent and if the farm has a high sulphate content in its water, this with the sulphur in the DDGS can add to the problems.
New products of Modified Wet Distillers together with solubles are now being developed and are proving to be an improved additive to cattle diet.
Dr Lardy added that as the biofuels industry is now looking at producing biodiesel from the fat in the corn, this will changed the nutritional content of the DDGS and WDGS and may allow for higher levels to be used in feed.
"The use of the fat for biodiesel will mean the product will have a higher protein and higher fibre content," Dr Lardy said.
One other positive test that has been carried out by the beef industry is on the flavour and tenderness of the beef fed on DDGS. To date, Dr Lardy said, shear force tests have shown no problems with tenderness and taste tests have shown no difficulties with flavour and texture.