PSVIII-3 Can the fermentation of insoluble corn fiber be improved in the pig? – An investigation into the in vivo mode of action of xylanase

Abstract

Abstract Xylanase may improve fermentability of corn co-products through the alteration of hemicellulose, but the mode of action (MOA) is incompletely understood. The experimental objective was to investigate the in vivo MOA of xylanase in growing pigs fed insoluble fiber. Sixty gilts (25.4 ± 0.9 kg BW; L337 X Camborough), were blocked by weight, housed individually, and randomly assigned to one of four dietary treatments: a low-fiber control (LF; 8.45% NDF), a 30% corn bran high-fiber control (HF; 24.5% NDF), HF + 100 mg of xylanase/kg (HF+XY; Econase XT 25P; AB Vista, Marlborough, UK), and HF + 50 mg of arabinoxylan-oligosaccharide/kg (HF+AX; 3-7 degrees of polymerization). Gilts were fed ad libitum for 36 d, followed by 10-d of metabolism crate housing and limit feeding (80% of average ad libitum intake). On d 46, pigs were necropsied and ileal, cecal, and colonic digesta were collected for short-chain fatty acid (SCFA) analysis, and 16s rRNA gene amplicon sequencing. Data were analyzed as a mixed model with random effects of replicate and block, and fixed effect of treatment. Differences in individual operational taxonomic units (OTUs) were compared using Linear Discriminant Analysis Effect Size. Acetate, propionate, butyrate, and total SCFA in the ileum did not differ (P >0.05), but HF+XY had 10 significantly different OTUs compared to HF in the ileum (P< 0.05). In the cecum, compared to LF, HF reduced total SCFA concentration (91.7 vs. 82.8 mM/L; P< 0.01). However, HF+XY and HF+AX increased total SCFA concentration by 23% and 12% over HF, respectively (P< 0.05). This is likely due to increased cecal acetate concentration (54.0, 53.2, 74.4, 61.2 mM/L for LF, HF, HF+XY, and HF+AX, respectively; P< 0.01). Total colonic SCFA concentration did not differ (P=0.72), but xylanase increased molar proportions of butyrate (P< 0.01). One MOA of xylanase could be the release of fermentable substrates from insoluble fiber.