Researchers at the University of Illinois are taking a closer look at the digestible energy of corn vs. distiller’s dried grains with soluble (DDGS) in growing pig diets.

“Previous research shows that while the amount of energy in DDGS is greater than that of corn, pigs have lower digestibility of energy in DDGS than in corn,” says Hans H. Stein, swine nutritionist at the university.

The biggest difference between corn and DDGS is fiber content. Fiber contributes to the total energy in DDGS, but not much is known about how pigs utilize that fiber. “We want to find ways to improve the utilization of this energy source, but first we need to understand the role of fiber in DDGS,” he explains.

Fiber is characterized as soluble or insoluble. The soluble fiber consists of pectins, hemicelluloses and oligosaccharides. “Soluble fiber will change the viscosity of the digesta in the intestinal tract while absorbing water and becoming easily fermentable in the intestinal tract,” he explains.

Insoluble fiber will not dissolve in solution and is made up of the hardest part of the plant, such as cellulose and lignin. These fibers do not change viscosity in the intestinal tract and they are the most difficult to ferment, he continues.

“Pigs utilize soluble fiber very well, almost 90%,” Unfortunately, most of the fiber in DDGS is insoluble and has a much lower digestibility. This is the reason for the low digestibility of the combined fiber fraction in DDGS,” he says.

The goal is to see if anything can be done to change the solubility of fiber, make it more soluble and, therefore, increase the utilization.

From a practical standpoint, DDGS’s higher insoluble fiber content means more undigested material goes straight into the manure, which increases manure management challenges for producers.

“If there is a higher fiber content in the manure, it creates thicker slurry, which could lead to more solids in the pit,” notes Matthew Robert, visiting research engineer in the university’s Department of Agricultural and Biological Engineering. Thicker slurry requires more agitation to get the solids in suspension and ready for pumping. Inadequate agitation leaves more solids in the pit, thus reduces pit storage capacity.

The Illinois research team’s study also opened doors to new research methods. “Fiber can be measured in many ways. One of the standard methods of measurement, Total Dietary Fiber (TDF), is very expensive. We found a less expensive procedure, Neutral Detergent Fiber (NDF), to be quite effective and very closely correlated to TDF,” Stein notes.

This finding can help stretch research dollars as they continue to look for ways to increase the solubility of fiber and, thus, find new ways to reduce the feed required to produce a pound of gain, Stein says.

The research report, “Digestibility of Dietary Fiber in Distillers Coproducts Fed to Growing Pigs,” was published in the July 2010 edition of the Journal of Animal Science, by Pedro E. Urriola and Stein, University of Illinois, and Jerry C. Shurson, University of Minnesota. Funding was provided by the National Pork Board and the Minnesota Pork Producers Association.