Impact of Fiber-Degrading Enzymes on Microbial Composition and NSP Metabolites in Nursery Pigs Fed a Higher Fiber Diet

The addition of fiber-degrading enzymes to high fiber diets may modulate intestinal microbial populations and non-starch polysaccharide (NSP) metabolites due to fiber degradation. This experiment was conducted to evaluate the effects of dietary xylanase (X; Huvepharma Inc.) and an enzyme blend (EB: cellulase, ß-glucanase, and xylanase; Huvepharma Inc.) on intestinal microbial populations and metabolites of weaned piglets fed a higher fiber diet. A total of 460 pigs (6.43±0.06 kg BW; F25 Genetiporc×6.0 Genetiporc) were blocked by weight and randomly assigned to 4 treatments, in a 2×2 factorial arrangement: X (0 vs 0.01%) and EB (0 vs 0.01%). There were 12 blocks and 48 pens. Diets were based on corn, soybean meal plus corn DDGS and wheat middlings at 5 or 10% each for wk 1-2 or 3-4, respectively. Digesta was collected on d 28 to determine microbial populations and fermentation products. Total bacteria 16S rRNA gene copy numbers were quantified using qPCR. Specific bacterial relative abundance was expressed as a proportion of total bacteria. Data were analyzed using PROC MIXED (SAS, 9.4) with pen as the experimental unit. Xylanase, EB and X*EB interaction were considered fixed effects. No interactions between X and EB on cecal VFA concentration were observed. The EB decreased (P<0.05) cecal propionate, butyrate, valerate, and total VFA (129.52 vs. 142.94 μM/g) compared with no EB. Xylanase had no effect on any VFA in the cecum. In the colon, X increased isobutyrate and isovalerate concentrations (P<0.05) compared to diets without X. There was an X*EB interaction for colonic propionate concentration; in the absence of xylanase, EB decreased propionate compared to control (37.03 vs. 44.85 μM/g; P<0.05), but in the presence of xylanase, EB did not affect colonic propionate (X vs. X+EB; P>0.10). An X*EB interaction trend was also detected for colonic butyrate and total VFA; when xylanse was not present, EB tended to reduce their concentrations compared to control (P<0.10), whereas, when xylanase was present, EB had no impact (X vs. X+EB; P>0.10). The EB tended to reduce the relative abundance of Enterobacteriaceae family (P<0.10). Unexpectedly, EB reduced the relative abundance of Lactobacillus spp. (19.17 vs.27.12%; P<0.05) in the colon. In summary, EB decreased total VFA concentration in the cecum and relative abundance of Lactobacillus spp. in the colon. This might indicate that pigs fed EB diets had less substrate for microbes in the large intestine compared to those fed diets without EB.