Of the 1.7 million litres of ethanol fermented in Canadian plants in 2009, 67 per cent came from corn and the rest from wheat or a corn-wheat blend. At this level the plants generate about 450,000 tonnes of wheat and wheat-corn DDGS (dried distillers grains with solubles) and about 900,000 tonnes of corn DDGS. On top of this, Canadians imported more than 800,000 tonnes of corn DDGS in 2009.
All of this begs the question: which provides the best value, corn or wheat DDGS? A recent University of Saskatchewan study by graduate student Lee-Anne Walter in collaboration with Agriculture and Agri-Food Canada scientists at Lethbridge and Lacombe looked into this question. It also revealed that including DDGS in the ration has implications for manure handling because of the significant increase in consumption and increased excretion of nitrogen and phosphorus.
When starch is removed from the grain during ethanol production, the nutrients that are left become concentrated in the DDGS. Feed testing is recommended because of the considerable variability in the protein, neutral detergent fibre (NDF) and sulphur due to differences in the grain and ethanol production processes.
Walter fed steers a standard control diet of 85 per cent barley grain, 10 per cent barley silage and five per cent supplement and compared the results to cattle fed wheat or corn DDGS instead of barley at 20 and 40 per cent of the diet dry matter.
The most notable change in the diet was the significant increase in protein and phosphorus, particularly at 40 per cent DDGS, and a tripling of the crude fat content with 40 per cent corn DDGS.
The steers averaged 376 kilograms at the start and finished around 649 (1,200 pounds).
Dry matter intake and average daily gain were similar to barley on the 20 per cent wheat DDGS diet, but intake and gain picked up on the 40 per cent ration. These steers also finished a few days faster than the controls, although feed efficiency ratings were basically the same.
The big news however was posted by steers on 40 per cent corn DDGS. They consumed only 85 per cent of the dry matter eaten by the controls, yet gained at a similar rate giving them superior feed efficiency.
The enhanced performance was attributed to the high fat content of corn DDGS, double that of the wheat, which supplied significantly more energy in the diet.
Both DDGS rations beat barley in terms of efficiency that translated into lower costs per pound of gain.
At 2008 prices including processing and transportation with barley at $200 per tonne, the control diet worked out to $421.62 per animal, or 70 cents per pound of gain.
Corn DDGS purchased at $228 per tonne that year produced a total ration cost of $405.33 per animal and 68 cents per pound of gain at the 20 per cent level. However, the biggest payoff was realized when corn DDGS replaced 40 per cent of the barley grain. The total feed cost was $352.80 per animal, while the cost per pound of gain dropped to 59 cents.
Wheat DDGS was priced lower at $192 per tonne but the higher consumption rate resulted in a total feed cost of $398.61 per animal when it replaced 20 per cent of the barley grain and $387.97 or 66 cents per pound of gain at the 40 per cent rate.
Substituting barley grain with either corn or wheat DDGS in the ration results in overfeeding protein and phosphorus, explains ruminant nutritionist John McKinnon who holds the University of Saskatchewan beef chair. In most cases cattle can handle this excess without any difficulty, however it does spill over into the manure and that has implications for cropland and pastures.
As the amount of DDGS in the ration increased, there was a corresponding increase in the amount of nitrogen and phosphorus excreted in the urine and feces. The results were more pronounced with wheat DDGS as it is higher in protein than corn DDGS.