160 Can growth performance, digesta characteristics, and oxidative status of swine fed diets high in insoluble fiber be improved? An investigation into the mode of action of xylanase

Xylanase may improve the utilization of insoluble fiber by the pig, but its mode of action (MOA) is incompletely understood. The experimental objective was to investigate xylanase MOA in vivo in growing pigs fed a diet higher in insoluble fiber. Sixty gilts (n = 15 pigs/treatment; 25.43 ± 0.88 kg BW; L337 X Camborough, PIC, Hendersonville, TN) were blocked by weight, housed individually, and randomly assigned to one of four dietary treatments: a low-fiber control (LF; NDF=8.45%), a 30% corn bran higher-fiber control (HF; NDF=24.5%), HF + 100 mg xylanase/kg (HF+XY; Econase XT 25P; AB Vista, Marlborough, UK), and HF + 50 mg arabinoxylan-oligosaccharide/kg (HF+AX; 3–7 degrees of polymerization). Gilts were fed ad libitum for 36 d, followed by a 10-d period of being limit fed (80% of average ad libitum intake) and housed in metabolism crates for use in a related study. Pigs and feeders were weighed on d 0 and 36. On d 46, pigs were necropsied and ileal, cecal, and colonic digesta pH were measured; serum was collected for malondialdehyde (MDA) and total antioxidant capacity (TAC) analysis. Data were analyzed using PROC MIXED (SAS; 9.4) as a randomized complete block design with pig as the experimental unit, block and replicate as random effects, and treatment as a fixed effect. Insoluble fiber reduced ADG (858 vs. 698 g/d; LF vs. HF, P < 0.001) and GF (0.433 vs. 0.353; LF vs. HF, P < 0.001), but not ADFI (P > 0.05). Xylanase, but not arabinoxylan-oligosaccharide, when compared to HF, improved ADG (762 vs. 698 g/d; P < 0.05), GF (0.382 vs. 0.353; P < 0.05), and final BW (P < 0.05). Cecal and colonic pH did not differ (P > 0.05), but LF and HF+XY reduced ileal pH (P < 0.05). Xylanase supplementation increased serum TAC (P < 0.05), and tended to reduce MDA (P = 0.098). In conclusion, xylanase supplementation improved insoluble fiber utilization. The MOA could include mitigation of reactive oxygen species.