In an effort to improve profitability, U.S. ethanol plants have been extracting increasing amounts of oil from corn dried distillers grains with solubles for sale into the biodiesel industry.

Dr Gerald Shurson an animal science professor with the University of Minnesota, says DDGS has always been a fairly variable ingredient and now the extraction of oil is making this ingredient even more variable.

Dr Shurson said: "We know that the oil content of DDGS does not accurately predict its energy value because fibre plays a pretty big role in this as well.

"The way we've attempted to come up with ways of estimating the change in energy value is to develop what we call prediction equations where we can actually measure different chemical components such as the fibre content or the gross energy content and from that we can develop a fairly accurate estimate of what the energy value of that particular source might be regardless of its oil content.

"We know that the energy value is going to change. There is not an easy way to relate oil content to the energy value but, on the positive side, by taking some of the oil out we can feed either higher levels of this ingredient and have less of a negative impact on pork fat quality or, often times we talk about reducing pork fat firmness, or we can continue feeding the typical levels and have a positive effect on that as well.

Dr Shurson says we have to realize DDGS is primarily an energy source so energy estimates have to be as accurate possible in order to extract their full value.

Dr Shurson concludes that some preliminary results suggest the levels digestible amino acids in oil extracted corn DDGS might be slightly reduced as well so we also need to pay attention to the digestible amino acid content.