In extrusion, cereal grains are processed under conditions of heat and pressure. Like other types of heat treatment, extrusion may reduce the concentration of antinutritional factors. Extrusion also gelatinizes starch, improving its digestibility. Improved digestibility of starch should, in turn, lead to an increase in digestible energy. Extrusion has also been shown in some studies to solubilize the insoluble fraction of the fiber which would also increase fiber digestibility and digestible energy.

Corn is a high starch ingredient, while oats are high in fiber. An experiment was conducted to determine the effects of extruding corn and oats on the apparent total tract digestibility (ATTD) of energy and fiber when fed to growing pigs.

Cervantes-Pahm, S. K., Y. Liu, and H. H. Stein. 2014. Comparative digestibility of energy and nutrients and fermentability of dietary fiber in eight cereal grains fed to pigs. J. Sci. Food Agric. 94:841–849. Link to full text (.pdf)

Cervantes-Pahm, S. K. and H. H. Stein. 2011. Metabolizable energy and digestibility of carbohydrates in cereal grains fed to growing pigs. J. Anim. Sci. 89(E-Suppl. 1):332-333 (Abstr.) Link to abstract (.pdf)

Stein, H. H. 2011. Energy and nutrient concentration and digestibility in alternative feed ingredients and recommended inclusion rates. In Proceedings of the American Association of Swine Veterinarians 42nd Annual Meeting. Phoenix, AZ. Link to full text (.pdf)