Wheat by-products are feedstuffs that
vary in nutritional value, partly because of arabinoxylans
that limit nutrient digestibility. Millrun is a byproduct
from dry milling wheat into flour and contains
varying amounts of the bran, middlings, screening, and
shorts fractions. The digestible nutrient content of millrun
is not well known. Effects of xylanase supplementation
(0 or 4,000 units/kg of diet) on energy, AA, P,
and Ca digestibilities were studied in a wheat control
diet and 5 diets containing 30% of a by-product (millrun,
middlings, shorts, screening, or bran) in a 2 × 6
factorial arrangement of treatments. The wheat control
diet was formulated to contain 3.34 Mcal of DE/kg and
3.0 g of standardized ileal digestible Lys/Mcal of DE.
Diets contained 0.4% chromic oxide. Each of 12 ilealcannulated
pigs (32.5 ± 2.5 kg) was fed 6 or 7 of 12
diets at 3 times the DE requirement for maintenance in
successive 10-d periods for 6 or 7 observations per diet.
Feces and ileal digesta were each collected for 2 d. Xylanase
tended to increase (P < 0.10) ileal energy digestibility by 2.2 percentage units and the DE content by 0.10 Mcal/kg of DM and increased (P < 0.05) ileal DM digestibility by 2.8 percentage units; a diet × xylanase interaction was not observed. Xylanase increased (P < 0.05) total tract energy and DM digestibilities and the DE content. A diet × xylanase interaction was observed; xylanase increased (P < 0.05) total tract energy digestibility of the millrun diet from 72.1 to 78.9%, DE content from 3.19 to 3.51 Mcal/kg of DM, and DM digestibility from 71.5 to 78.6%. Diet affected (P < 0.05) and xylanase improved (P < 0.05) digestibility and digestible contents of some AA in diets and by-products, including Lys, Thr, and Val. Xylanase increased (P < 0.05) Lys digestibility by 13.8, 5.0, 5.2, 6.0, and 14.1 percentage units in millrun, middlings, shorts, screening, and bran, respectively. Diet affected (P < 0.01) total tract P and Ca digestibilities. Xylanase increased (P < 0.05) digestible P and Ca contents. In summary, nutrient digestibility varies among wheat by-products. Millrun contained 2.65 Mcal of DE/kg of DM, which xylanase increased to 3.56 Mcal of DE/kg of DM. Xylanase improved nutrient digestibility and DE content in wheat by-products; and the extent of improvement depended on the by-product. Xylanase supplementation may maximize opportunities to include wheat byproducts in swine diets and ameliorate reductions in nutrient digestibility that may be associated with arabinoxylans.