Effect of xylanase and β-glucanase on growth performance, activity of digestive enzymes, digestibility, and microbiome diversity of juvenile Nile tilapia fed soybean meal and/or sorghum distillers dried grains with solubles-based diets

Abstract

Recent studies have identified the advantage of supplementing exogenous enzymes targeting non-starch polysaccharides (NSPs) to surmount the problem caused by high-fiber plant-based diets containing distillers' dried grains with solubles (DDGS). This research investigated the effects of supplementing a blend of xylanase and β-glucanase (XB) in diets containing soybean meal (SBM) and/or sorghum distillers dried grains with solubles (DDGS) on growth performance, blood biochemical parameters, activity of digestive enzymes, apparent digestibility coefficients (ADCs) and microbiome of juvenile Nile tilapia, Oreochromis niloticus. Fish (n = 192; 12.09 ± 0.43 g) were randomly assigned in a 2 × 2 factorial design, and fed diets comprised of two main protein sources [SBM or SBM plus DDGS (SBM/DDGS)] either not supplemented (−XB) or supplemented with XB (+XB; 0.2 g kg−1 diet) with four replicates in each group and 12 fish per replicate. Liquid XB blend was top-sprayed onto extruded diets containing 17.6 MJ kg−1 gross energy and 313.6 g kg − 1 crude protein to provide 1120 TXU kg−1 of endo-1,4-β-xylanase and 500 TGU kg−1 diet of endo-1,4-β-glucanase. Fish were stocked into 70-L aquaria in a recirculating aquaculture system with a water flow of 0.5 L s−1 and temperature set at 28 °C throughout the trial. Fish were hand-fed six times daily until apparent satiety for 56 days. There was no interaction between protein source and XB, and fish fed the SBM diets had higher body weight gain, feed efficiency ratio, energy retention efficiency and protein retention efficiency compared to those fed SBM/DDGS diets. XB promoted higher body weight gain (+12.5%), feed efficiency ratio (+3.4%) and energy retention efficiency (+8.6%) aligned with increased activity of amylase (+32.0%) and lipase (+15.1%) enzymes in the gut than those fed the −XB diets. An interaction effect identified higher digestible energy (DE; +2.1 MJ kg−1 diet) contents in the SBM/DDGS diet with XB compared to the other diets. Analysis of the “core microbiota” revealed that Fusobacteria (Cetobacterium) dominated gut microbiota, irrespective of dietary treatment. Additionally, XB supplementation increased the bacterial diversity by quantifying operational taxonomic units (OTUs) regardless of the main dietary protein. Notably, fish fed the SBM/DDGS diets revealed a higher abundance of beneficial bacteria Proteobacter (Plesiomonas) and Firmicutes (Lactobacillus) than those fed diets of only SBM, irrespective of XB supplementation. Fish offered diet containing SBM/DDGS with XB had a higher abundance of Actinobacteria (Bifidocterium) than those fed other diets. Overall, this study found SBM to have higher nutritive value than DDGS, and supplementation of XB could alleviate the adverse effects of antinutritional factors in sorghum DDGS. Additionally, sorghum DDGS stimulated the abundance of beneficial bacteria in the gut microbiota.