URBANA, Ill. — Pork producers need accurate information on the energy value of fat in feed ingredients to ensure that diets are formulated economically and in a way that maximizes pork fat quality.

Researchers at the University of Illinois have determined the true ileal and total tract digestibility of fat in four corn co-products, as well as in full fat soybeans and corn oil.

Hans Stein, a professor of animal sciences at the U of I, led the team of researchers in the study in which they looked at four corn co-products — distillers dried grains with solubles, high-protein distillers dried grains, corn germ and a high-oil corn that contained about 7 percent lipids. They also tested full-fat soybeans and extracted corn oil.

Three diets were formulated containing each source of oil, as well as a basal diet that contained no added fat. These diets were fed to cannulated pigs.

The apparent ileal and total tract digestibility of lipids in each diet was calculated, and a regression procedure was used to estimate endogenous losses and to calculate the true ileal digestibility and the true total tract digestibility of lipids.

“We observed that the digestibility of oil in soybeans is much greater than in the corn co-products. It appears that pigs can utilize that oil much more easily,” Stein said.

He attributed this to differences in the way fat is stored in the ingredients.

“In soybeans, you have almost 20 percent fat, and therefore a lot of that fat is just stored as regular triglycerides and relatively easy to get to,” he said. “In the other ingredients, in particular the corn germ and the DDGS, some of the fat is encapsulated by fiber, which makes it more difficult for the enzymes to digest.”

According to study results, the true ileal digestibility of corn oil was greatest at 95.4 percent. Among intact sources of fat, the fat in full-fat soybeans at 85.2 percent and HP DDG at 76.5 percent was the most digestible.

Digestibility of fat was lowest in DDGS at 62.1 percent, high-oil corn at 53 percent and corn germ at 50.1 percent.

Corn oil also had the greatest true total tract digestibility at 94.3 percent. Full-fat soybeans had the next greatest digestibility at 79.7 percent.

HP DDG was next at 70.2 percent. Finally, DDGS at 51.9 percent, corn germ at 43.9 percent and high-oil corn at 41.4 percent had the lowest true total tract digestibility.

Stein said the results of the research were in agreement with several previous experiments indicating that the energy value of some ingredients was less than would be expected based on their lipid content.

“But now we have an explanation because we realize that pigs don’t digest those lipids very well, so it doesn’t necessarily help that these products have higher concentrations of oil,” he said.

“From a nutritional point of view, there would be a clear advantage if we could first extract the fat and then add it to the diet as corn oil rather than leave it in the ingredients. Whether such an approach would be economical would depend on the cost of extracting the oil from corn germ and other ingredients,” he added.

The study, “In growing pigs, the true ileal and total tract digestibility of acid hydrolyzed ether extract in extracted corn oil is greater than in intact sources of corn oil or soybean oil,” was published in the Journal of Animal Science and is available at www.journalofanimalscience.org/content/91/2/755.full.

Illinois graduates Beob Gyun Kim of Konkuk University and Dong Yong Kil of Chung-Ang University in Korea were co-authors of the study.