For their part, Shurson's research team hasn't found that to be true as long as the quality, nutrient content and digestibility of the DDGS source being used is known. The disparity in research results may reflect differences in quality of DDGS, or different approaches in diet formulation.

First, as with traditional corn-soy diets, it's important to start with good quality distiller's grains. Pay for the good stuff. Last fall the price was $75/ton. Now with added demand and limited availability, the price is $125-135/ton — if you can get it, he states.

Get to know your supplier. Build a good relationship. Have samples tested by an outside, third-party laboratory to determine the nutrient content and quality of the DDGS you're going to buy.

Plus, ask your supplier to “level with you” if a bad batch of distiller's has been produced at your local ethanol plant, Shurson says.

Shurson says discussions involving DDGS and pork quality research trials at Minnesota basically center on four major issues:

• Dressing percentage or yield slightly declines as pigs are fed the higher rates of DDGS. Figure 1 shows that the percentage of carcass yield starts to fall at 20% and 30% dietary levels. However, the percentage of carcass lean tends to increase at 30% DDGS vs. the control diet ( Figure 2).

• Belly fat becomes less firm when higher levels of DDGS are fed ( Figure 3). That is attributed to the higher level of unsaturated fatty acids, especially linoleic acid, that is found in corn oil. Softer fat results from the high amounts of unsaturated fatty acids in the diet.

• The pork industry needs to discuss endpoint measurements in reevaluating maximum inclusion rates of DDGS in swine diets. The most common measurement associated with pork fat quality being discussed in the industry is iodine value, which Shurson explains is simply the ratio of unsaturated fatty acids to saturated fatty acids in pork fat. The higher the number, the greater the proportion of unsaturated fatty acids compared to saturated fatty acids.

Some have suggested the maximum iodine value should be 72. The Danes have suggested it should be 70. Nothing has been clearly defined in the U.S. swine industry. “A corn-soy diet in the United States would produce a backfat iodine value of about 67,” he says.

“For every 10% you increase distiller's grains, you increase your iodine value by about 1.5 points,” he says. Shurson's group reports that in one of four recent studies at the University of Minnesota, feeding 30% DDGS still produced an acceptable iodine level of 72.

Granted, in one of their four studies, higher levels of DDGS slightly reduced loin firmness and marbling scores, as shown in Figure 4, but they were still within acceptable standards published by the National Pork Producers Council, he emphasizes.

But a recent consumer taste panel who ate pork loins from pigs fed diets containing 30, 20, 10 and 0% DDGS couldn't detect any appreciable differences between the various products (See Figure 5), Shurson adds.

• The fourth major issue is if distiller's grains makes pork fat softer and more unsaturated, does that in turn make the product more susceptible to rancidity or lipid oxidation and reduce its shelf life?

To answer that question, Shurson's research team partnered with Hormel Foods and evaluated carcasses from hogs fed diets containing up to 30% DDGS, processed and packaged pork loin or chops in retail packages and stored in retail-type temperatures and conditions for 28 days.

“At the end of the 28 days, we saw no differences among treatments, and results tested at about half of what the minimum amount would be to indicate for oxidative rancidity,” he says.