Nutrient composition and digestibility by growing pigs of amino acids and energy vary between wheat middlings from Europe and the United States

Two experiments were conducted to test the hypothesis that there are no differences in composition, apparent total tract digestibility (ATTD) of gross energy (GE), or standardized ileal digestibility (SID) of amino acids (AA) in wheat middlings sourced from flour mills in Europe or in the U.S. For both experiments, ten sources of wheat middlings were used. Five sources were procured from Europe and the other five sources were procured from the U.S. The ten sources of wheat middlings varied in starch from 79 to 286 g/kg (as-fed) and total dietary fiber varied from 324 to 508 g/kg. In experiment 1, 88 castrated male pigs (27.2 ± 2.5 kg) were individually housed in metabolism crates and allotted to eleven diets with eight replicate pigs per diet. A corn-soybean meal diet and ten diets containing corn, soybean meal, and each source of wheat middlings as the only energy sources were formulated. Feces and urine were collected using the marker-to-marker approach with 5-day adaptation and 4-day collection periods. The ATTD of GE and the concentration of digestible energy (DE) in wheat middlings from one of the European sources were less (P < 0.05) than in the other sources. Likewise, wheat middlings from Europe had reduced concentrations of DE and metabolizable energy (12.10 and 11.42 MJ/kg, dry matter basis) compared with wheat middlings from the U.S (12.69 and 12.32 MJ/kg, dry matter basis). In experiment 2, eleven pigs (52.8 ± 3.6 kg) with a T-cannula in the distal ileum were allotted to an 11 × 8 Youden square design with eleven diets and eight periods resulting in eight replicates per diet. A nitrogen-free diet and ten diets containing each source of wheat middlings as the only AA-containing ingredient were formulated. Results indicated that the SID of most AA in wheat middlings from two of the European sources was less (P < 0.05) than in the other sources. As a consequence, the average SID of AA for wheat middling from Europe was less than the SID of AA in wheat middlings from the U.S. In conclusion, energy concentrations and AA digestibility values for wheat middling from Europe were less than in wheat middlings from the U.S., which is likely due to increased concentration of dietary fiber in wheat middlings from Europe. Greater variability in energy and AA digestibility values was also observed in the five sources of wheat middlings from Europe compared with wheat middlings from the U.S., which is possibly a result of differences among European flour mills in the production process.