Interactive effects of pelleting and particle size reduction of corn on ileal digestibility of starch, acid-hydrolyzed ether extract, and amino acids in corn-soybean meal diets fed to growing pigs

The objective was to test the hypothesis that pelleting and reducing corn particle size separately or in combination increase the apparent ileal digestibility (AID) of starch and acid-hydrolyzed ether extract (AEE) and standardized ileal digestibility (SID) of amino acids (AA) in diets fed to growing pigs. Six corn-soybean meal-based diets were formulated using three particle sizes of corn (i.e., 700, 500, or 300 μm) and two diet forms (i.e., meal or pelleted). A nitrogen-free diet was also used. Seven pigs (initial weight: 59.3 kg) that had a T-cannula installed in the distal ileum were allotted to the seven diets using a 7 × 7 Latin square design with 7 periods. Ileal digesta were collected for 2 days of each period. Results indicated that there were no interactions between particle size and diet form for the SID of AA. However, the AID of AEE was increased by reducing the particle size of corn, but the increase was greater in meal diets than in pelleted diets (interaction; P < 0.001). The AID of starch also was increased by reducing the particle size of corn in meal diets, but not in pelleted diets (tendency for an interaction; P = 0.060). Regardless of particle size, the ileal digestibility of AEE, starch, and most AA was greater (P < 0.05) in pelleted diets than in meal diets. Regardless of diet form, the ileal digestibility of AEE, starch, and most AA increased (linear; P < 0.05) by reducing the particle size of corn. In conclusion, reducing corn particle size affects starch and AEE digestibility differently in meal and pelleted diets, but both pelleting and reducing particle size increase the AA digestibility.