Exogenous enzymes may improve the fermentability of dietary fiber in swine diets by hydrolyzing non-starch polysaccharides into oligosaccharides and sugars. In particular, the enzyme xylanase hydrolyzes the β-(1-4) glycosidic bonds between the xylose units in the backbone of arabinoxylans in cereal grains and grain coproducts, resulting in the release of a combination of xylose, arabinose, and xylo-oligosaccharides from arabinoxylans that can be fermented by pigs. Previous data indicate that xylanase increased the degradation of dietary fiber and increased energy digestibility in diets for growing pigs; however, there are limited data for the impact of xylanase on energy and fiber digestibility in gestating and lactating sows. Therefore, an experiment was conducted to test the hypothesis that exogenous xylanase added to diets for gestating and lactating sows will increase the apparent total tract digestibility (ATTD) of gross energy and total dietary fiber (TDF), and increase the concentrations of digestible energy (DE) and metabolizable energy (ME) during two reproductive cycles.