Digestibility of amino acids, fiber, and energy by growing pigs, and concentrations of digestible and metabolizable energy in yellow dent corn, hard red winter wheat, and sorghum may be influenced by extrusion

Two experiments were conducted to determine effects of extrusion on energy and nutrient digestibility in cereal grains fed to growing pigs. One source of yellow dent corn, one source of hard red winter wheat, and one source of sorghum were ground to approximately 300 microns and each source of grain was divided into 2 batches. One batch of each grain was extruded, whereas the other batch was used without further processing. In Exp. 1, 7 diets were formulated to determine ileal starch and amino acid (AA) digestibility in the grains. Three diets contained the non-extruded grains and 3 diets contained the extruded grains. The last diet was an N-free diet that was used to determine basal endogenous losses of AA from the pigs. Seven growing barrows (initial body weight = 14.2 ± 0.9 kg) had a T-cannula installed in the distal ileum and were allotted to a 7 × 7 Latin square. Each experimental period lasted 7 days with the initial 5 days being the adaptation period and ileal digesta were collected on days 6 and 7. Results indicated that extruded grains had greater (P < 0.001) apparent ileal digestibility (AID) of starch than non-extruded grains. Extrusion also increased standardized ileal digestibility (SID) of crude protein (CP) and all AA except Lys and Pro in corn, but the SID of CP and AA in wheat and sorghum was not affected by extrusion. In Exp. 2, 6 diets were used. Three diets contained the non-extruded corn, wheat, or sorghum, and 3 diets contained the extruded grains. Forty eight growing barrows (initial body weight = 15.1 ± 3.7 kg) were allotted to a randomized complete block design. Pigs were housed individually in metabolism crates and feces and urine were collected separately for 5 days after 5 days of adaptation. The apparent total tract digestibility (ATTD) of gross energy was increased by extrusion of corn or sorghum, but that was not the case for wheat (interaction, P < 0.001). The ATTD of neutral detergent fiber in wheat was reduced by extrusion, but not in corn and sorghum (interaction, P < 0.001). However, extrusion reduced (P < 0.05) the ATTD of acid detergent fiber in all grains. Extrusion increased the digestible energy (DE) and metabolizable energy (ME) in corn and sorghum (DM-basis) compared with non-extruded grains, but there was no increase in DE and ME (DM-basis) if wheat was extruded (interaction, P < 0.001). In conclusion, extrusion increased the AID of starch in all grains and the ATTD of energy and the DE and ME in corn and sorghum. The SID of most AA in corn was also increased by extrusion.