When evaluating the energy content of pig diets, producers and feed companies in the United States usually use the digestible energy (DE) and metabolizable energy (ME) systems. However, these systems do not take into account the heat produced by the animals during digestion, and thus the energy lost by pigs in the process of digesting and metabolizing the feed. Pigs fed diets high in fiber have greater feed intake, larger gastrointestinal tracts, and increased hindgut fermentation relative to pigs fed diets containing less fiber. Therefore, they might be expected to have greater heat production as well. As a result, the DE and ME systems may overestimate the energy value of fibrous feed ingredients. Net energy (NE) takes heat production into account, and thus may be a more accurate estimate of the energy available to the pig.

An experiment was conducted to test the hypothesis that increasing dietary fiber in diets fed to growing pigs will increase heat production and decrease net energy values.