https://phys.org/news/2018-05-pigs-digest-fiber-efficiently-high.html

"Energy is obtained from dietary fiber via hindgut fermentation, and there may be a saturation point in the fermentation capacity in the hindgut of growing pigs," he says. "Increasing dietary fiber also makes feed move through the digestive tract more quickly, so there's less time for it to ferment."

Stein and fellow researchers, Diego Navarro of U of I and Erik Bruininx and Lineke de Jong of Agrifirm Innovation Center, tested ten diets fed to growing pigs. The diets were formulated by adding either 15 or 30 percent canola meal, corn germ meal, sugar beet pulp, or wheat middlings to a basal diet consisting of corn, soybean meal, and cornstarch.