Xylanase supplementation in corn-based swine diets: a review with emphasis on potential mechanisms of action

Abstract

Corn is a common energy source in pig diets globally; when financially warranted, industrial corn co-products, such as corn distiller’s dried grains with solubles (DDGS), are also employed. The energy provided by corn stems largely from starch, with some contribution from protein, fat, and non-starch polysaccharides (NSP). When corn DDGS are used in the diet, it will reduce starch within the diet, increase dietary protein, fat, and NSP levels, and alter the source profile of dietary energy. Arabinoxylans comprise the majority of NSP in corn and its co-products. One strategy to mitigate the antinutritive effects of NSP and improve its contribution to energy is by including carbohydrases within the diet. Xylanase is a carbohydrase that targets the β-(1-4) glycosidic bonds of arabinoxylan, releasing a mixture of smaller polysaccharides, oligosaccharides, and pentoses that could potentially be used by the pig. Xylanase is consistently effective in poultry production and moderately consistent in wheat-based swine diets, but its efficacy in corn-based swine diets is quite variable. Xylanase has been shown to improve the digestibility of various components of swine-based diets, but this seldom translates into an improvement in growth performance. Indeed, a review of xylanase literature conducted herein suggest xylanase improves the digestibility of dietary fiber at least 50% of the time in pigs fed corn-based diets, but only 33% and 26% of the time was an increase in average daily gain or feed efficiency observed, respectively. Intriguingly, there has been an abundance of reports proposing xylanase alters intestinal barrier integrity, inflammatory responses, oxidative status, and other health markers in the pig. Notably, xylanase has shown to reduce mortality in both high and low health commercial herds. These inconsistencies in performance metrics, and unexpected health benefits, warrant greater understanding of the in vivo mechanism(s) of action (MOA) of xylanase. While the MOA of xylanase has been postulated considerably in the literature, and widely studied in in vitro settings, in wheat-based diets, and in poultry, there is a dearth of understanding of the in vivo MOA in pigs fed corn-based diets. This purpose of this review is to explore the role of xylanase in corn-based swine diets, discuss responses observed when supplemented in diets containing corn-based fiber, suggest potential MOA of xylanase, and identify critical research gaps.

The influence of xylanase on the fermentability, digestibility, and physicochemical properties of insoluble corn-based fiber along the gastrointestinal tract of growing pigs

“…There are contradicting reports on the efficacy of xylanase to improve nutrient and energy digestibility, fermentation, and growth performance in growing pigs ( Torres-Pitarch et al, 2019 ; Petry and Patience, 2020 ). These inconsistencies could be due to differences in enzyme characteristics, inadequate supplementation time, dietary fiber concentration, or the physicochemical properties of insoluble corn-based fiber ( Petry and Patience, 2020 ). Additionally, results of recent research suggest at least 25 d of adaptation may be needed for xylanase to improve fiber digestibility in the upper small intestine of pigs fed corn-based fiber ( Petry et al, 2020a ).…”

“…Likewise, there is evidence to suggest supplementing xylanase increases fiber solubility in the ileum ( Tiwari et al, 2018 ), and this soluble NSP fraction in the ileal effluent may subsequently alter digesta viscosity in the large intestine. However, the efficacy of xylanase in pigs fed corn-based diets is variable and not fully understood ( Petry and Patience, 2020 ).…”

Xylanase Supplementation Modulates the Microbiota of the Large Intestine of Pigs Fed Corn-Based Fiber by Means of a Stimbiotic Mechanism of Action

“…Microbial fermentation largely occurs in the cecum and colon due to the dense microbial populations in these gastrointestinal regions ( Jensen and Jørgensen, 1994 ). Additionally, there are increasing reports that supplementation of xylanase to swine benefits markers of improved gastrointestinal health, and commonly reduces finishing pig mortality in commercial production ( Petry and Patience, 2020 ). These improvements in health are often postulated to result from modulation of microbial populations in the gut.…”

“…It has been reported that these AXOS can be rapidly fermented by the resident microbiota and modulate the gastrointestinal microbiota in the large intestine of poultry via a stimbiotic MOA ( Bautil et al, 2020 ; González-Ortiz et al, 2020 ). However, there is a dearth of research in swine ( Petry and Patience, 2020 ). A stimbiotic was defined by González-Ortiz et al (2019) , as “ an additive that stimulates a fiber-degrading microbiome resulting in an increase in fiber fermentability even though the additive itself contributes little to short chain fatty acid production .” The proposed mechanism of a stimbiotic is that it accelerates the capacity of the large intestine to more efficiently digest fiber by modulating microbial taxa that produce their own carbohydrases ( Bautil et al, 2020 ; González-Ortiz et al, 2020 ).…”

Conversion of Wheat Bran to Xylanases and Dye Adsorbent by Streptomyces thermocarboxydus

“…Among them, endo-xylanase, and exo-xylanase are the most important contributors to xylan depolymerization. Until now, vast applications of xylanase have been extensively explored based on its ability in xylan degradation, for example, biofuels production [ 6 , 7 , 8 ], pulp and paper bleaching [ 9 , 10 , 11 ], bioactive compounds [ 12 , 13 , 14 ], animal feed [ 15 , 16 ], and baking [ 17 , 18 , 19 ].…”