Effects of dietary particle size and fiber source on nutrient digestibility and short chain fatty acid production in cannulated growing pigs

The objective of this study was to evaluate the effects of different feed particle sizes and fiber sources on nutrient digestibility and short chain fatty acids (SCFA) concentration in different intestinal segments of pigs. Eighteen barrows with T-cannula in the distal ileum were randomly allotted to a 3 x 2 factorial arrangement with 3 different high-fiber diets including corn bran (CB), sugar beet pulp (SBP) and soybean hulls (SH), and 2 different feed particle sizes. The experiment contained 2 periods, and each period lasted for 15 days, including 10 days for diets adaptation, 3 days for fecal collection, and 2 days for ileal digesta collection. The results indicated that coarse diets decreased (P < 0.05) the apparent ileal digestibility (AID) of gross energy (GE), dry matter (DM), organic matter (OM), total dietary fiber (TDF) and insoluble dietary fiber (IDF), but tended to increase (P < 0.10) the hindgut disappearance of GE. Feed particle sizes did not affect the apparent total tract digestibility (ATTD) of dietary nutrients except for ether extract (EE), the AID of amino acid (AA) and SCFA concentrations in ileal digesta, but fiber sources had significant effects on (P < 0.05) the AID, ATTD and hindgut disappearance of most nutrients in diets and the fecal SCFA concentrations. Moreover, there were interactive effects (P < 0.05) between particle sizes and fiber sources on the hindgut disappearance of fiber fractions. Coarse CB diets increased (P < 0.05) the hindgut disappearance of TDF, soluble dietary fiber (SDF), IDF, neutral detergent fiber (aNDF), acid detergent fiber (ADF) and cellulose, but the different particle size of SBP and SH did not affect the hindgut disappearance of TDF, ADF and cellulose. In conclusion, particle size mainly affected the ileal digestibility of nutrients and fiber fractions in pigs, but had few effects on their whole gastrointestinal digestibility, and these influences varied among different dietary fiber sources.