Nutrient composition and digestibility of energy and nutrients in wheat middlings and red dog fed to growing pigs.

This experiment was designed to determine nutrient composition and apparent total tract digestibility (ATTD) of GE, DM, OM, and NDF and the concentration of DE and ME in 10 sources of wheat middlings and in 1 source of red dog that were obtained from different flour mills in the United States. Twelve growing pigs (initial BW: 31.0 ± 1.0 kg) were randomly allotted to a 12 × 8 Youden square design with 12 dietary treatments and eight 14 d periods. Pigs were individually housed in metabolism crates for total collection of feces and urine. A basal diet based on corn and soybean meal, and 11 diets containing corn, soybean meal, and 39.4% of one of the 10 sources of wheat middlings or of red dog were formulated. The ATTD of GE, DM, OM, and NDF in all diets was calculated using the direct procedure, and the ATTD of GE, DM, OM, and NDF in each source of wheat middlings or red dog was calculated by difference. Values for DE and ME were calculated as well. The average concentration of CP was 17.67% in wheat midlings and 17.0% in red dog, and the concentration of acid hydrolyzed ether extract (AEE) and total dietary fiber (TDF) was 2.44 and 13.90% in red dog, but 4.07 and 36.45% in wheat middlings. Red dog also contained more starch (42.98%) than wheat middlings (20.28%). Red dog had greater bulk density (498.5 g/L) and smaller particle size (146 µm) compared with wheat middlings (315.1 g/L and 783 µm). The average ATTD of GE, DM, OM, and NDF in wheat middlings (67.2%, 71.2%, 72.9%, and 53.0%, respectively) was less (P < 0.05) than in red dog (79.35%, 82.9%, 86.6%, and 58.7%, respectively). The average concentrations of DE and ME in wheat middlings were 2,990 and 2,893 kcal/kg DM, and these values were less (P < 0.05) than the DE and ME in red dog (3,408 and 3,292 kcal/kg DM). In conclusion, wheat middlings contains more fiber and less starch than red dog and the ATTD of GE and nutrients is greater in red dog than in wheat middlings. As a consequence, concentrations of DE and ME are greater in red dog than in wheat middlings.