Abstract
This research tested the hypothesis that xylanase modulates microbial communities within the large intestine of growing pigs fed corn-based fiber through a stimbiotic mechanism(s) of action (MOA). Sixty gilts were blocked by initial body weight, individually housed, and randomly assigned to one of four dietary treatments (n = 15): a low-fiber (LF) control, a high-fiber (HF) control containing 30% corn bran, HF+100 mg/kg xylanase (HF+XY), and HF+50 mg/kg arabinoxylan-oligosaccharide (HF+AX). Pigs were fed dietary treatments for 46 days. On day 46, pigs were euthanized, and mucosa and lumen contents were collected from the cecum and the colon. The V4 region of 16S rRNA genes was sequenced and clustered into 5,889, 4,657, 2,822, and 4,516 operational taxonomic units (OTUs), in the cecal contents and mucosa and colonic contents and mucosa, respectively. In cecal contents, HF+XY increased measures of α-diversity compared to LF (p < 0.001). Relative to LF, HF increased the prevalence of 44, 36, 26, and 8, and decreased 19, 9, 21, and 10, of the 200 most abundant OTUs from the cecal contents and mucosa and colonic contents and mucosa, respectively (Q < 0.05). Compared to LF, HF increased the abundance of OTUs from the Treponema_2, Ruminococcus_1 genera, from the Lachnospiraceae, Ruminococcaceae, and Prevotellaceae families. In contrast, relative to LF, HF decreased Turicibacter and Lactobacillus in the cecal contents, and Megasphaera and Streptococcus in the mucosa. Relative to HF, HF+XY increased 32, 16, 29, and 19 and decreased 27, 11, 15, and 10 of the 200 most abundant OTUs from the cecal contents and mucosa and colonic contents and mucosa, respectively (Q < 0.05). The addition of xylanase to HF further increased the abundance of OTUs from the Lachnospiraceae and Ruminococcaceae families across the large intestine. Compared to HF, HF+XY increased the abundance of Lactobacillus, Bifidobacterium, and Faecalibacterium among all locations (Q < 0.05). However, HF+AX did not increase the prevalence of these genera in the large intestine. Supplementing xylanase to HF increased hidden-state predictions of microbial enzymes associated with arabinoxylan degradation, xylose metabolism, and short-chain fatty acid production. These data suggest xylanase elicits a stimbiotic MOA in the large intestine of pigs fed corn-based fiber.
Highlights
It is well established that pigs do not synthesize the endogenous enzymes required to digest dietary fiber (DF)
Gilts were blocked by initial body weight and randomly assigned within a block to one of four dietary treatments: a low-fiber (LF) control with 7.5% neutral detergent fiber (NDF), a high-fiber (HF) control with 30% corn bran without solubles (NDF = 21.9%), HF+100 mg xylanase/kg (HF+XY; Econase XT 25P; AB Vista, Marlborough, United Kingdom) providing 16,000 birch xylan units per kg, and HF+50 mg arabinoxylanoligosaccharide/kg (HF+AX; 3–7 degrees of polymerization)
Cecum From cecal content samples, a total of 2,707,536 high-quality reads were clustered into 5,889 operational taxonomic units (OTUs) and 213 genera, with a median of 41,672 sequences among samples
Summary
It is well established that pigs do not synthesize the endogenous enzymes required to digest dietary fiber (DF). Modern swine diets are trending to contain increased concentrations of DF. This is often a consequence of mitigating rising feed costs by utilizing economically-priced industrial co-products. Many of these co-products fed to pigs are corn-based, and often shift the carbohydrate composition of the diet to favor DF, rather than starch (Acosta et al, 2020). It is well known that increasing DF can reduce nutrient and energy digestibility, impair hindgut fermentation, and decrease pig performance (Gutierrez et al, 2013; Weber et al, 2015). Corn-based arabinoxylans are poorly fermented by resident microbiota due to their structural complexity and poor solubility (Bach Knudsen, 2014). One potential strategy to improve the fermentability of DF, and possibly mitigate its negative effects, is to include exogenous carbohydrases into the diet
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