253 The influence of corn-based fiber on digesta short chain fatty acid composition and pH in growing pigs

Abstract

Abstract Pigs can obtain energy from fibrous feedstuffs through a symbiotic relationship with their gastrointestinal microbiome, which results in the production of metabolites, such as short chain fatty acids (SCFA). An experiment was conducted with the objective of investigating how different insoluble corn-based fiber sources influence changes in SCFA composition along the digestive tract of growing pigs. Two replicates of 28 gilts [n = 56; initial body weight (BW) = 26.7 ± 2.5 kg; PIC800 x Camborough], were randomly assigned to one of 7 semi-synthetic diets. Dietary treatments included a control (CTL) diet with a formulated total dietary fiber (TDF) value of < 1% and 6 diets with a CBF replacing 30% of the corn starch in CTL: dehulled degermed corn (DHDG; TDF = 1.09%), ground corn (COR; TDF = 3.24%), high protein dried distiller’s grains (HP; TDF = 8.79%), dried distiller’s grains (DDGS; TDF = 9.35%), corn gluten meal (CGM; TDF = 9.88%), and corn bran (BRN; TDF = 13.15%). Pigs were individually housed, and limit-fed at 2.4 times maintenance. On d 31, pigs were necropsied, and ileal, cecal, and colonic digesta were collected for immediate SCFA analysis and stomach, jejunal, ileal, and cecal digesta pH was measured. Data were analyzed as a linear mixed model with treatment as a fixed effect, replicate as a random slope or fixed effect, where appropriate, using the mixed procedure of SAS. There were no differences in jejunal nor stomach pH (P ≥ 0.51). Ileal pH was greatest (P = 0.01) in HP, DDGS, and CGM diets. Cecal pH was greatest (P < 0.01) in the BRN diet and lowest in COR and HP. Molar proportions of ileal SCFAs did not differ (P ≥ 0.74) among treatments. In the cecum, molar proportions of butyrate production did not differ (P = 0.74). Cecal acetate proportions were less (P = 0.03) in CTL, COR, and HP compared with all other treatments (51.54, 61.09, 51.92, 52.89, 59.16, 63.87, and 63.32%, for CTL, DHDG, COR, HP, DDGS, CGM, and BRN, respectively). Cecal propionate proportions were greatest (P = 0.01) in BRN and least in DHDG, COR, and CGM (30.85, 27.67, 27.67, 30.91, 30.47, 24.03, and 35.86% for CTL, DHDG, COR, HP, DDGS, CGM, and BRN, respectively). Relative to CTL, isobutyrate proportions in the cecum for COR, HP, and DDGS were reduced by 65%, 52%, and 53%, respectively (P < 0.01). In the colon, there were no differences in molar proportions of acetate, butyrate, nor isobutyrate (P ≥ 0.254). However, HP and CGM had a smaller (P = 0.04) proportion of propionate in the colon and COR and BRN had the greatest proportion of colonic propionate (33.92, 29.68, 38.41, 25.3, 30.00, 26.76, and 37.94% for CTL, DHDG, COR, HP, DDGS, CGM, and BRN, respectively). Collectively, the different fibrous components of CBFs can influence SCFA proportions in the growing pig.