Xylanase and β-glucanase improve growth performance, gut barrier, and microbiota of pre-growout Nile tilapia, Oreochromis niloticus fed a vegetable-based diet

Abstract

A 90-day study was conducted to evaluate the effects of the top-sprayed xylanase-β-glucanase (XB) blend on the growth performance, blood parameters, gut morphology, and intestinal microbiome in pre-growout Nile tilapia, Oreochromis niloticus. Fish (n = 136; initial body weight 12.0 ± 1.4 g; 70 days of age) were randomly distributed in an entirely randomly design with two levels of XB supplementation, being not supplemented (Control) and supplemented at 0.2 g kg−1 diet, containing analyzed 1130 TXU kg−1 diet of endo-1,4-β-xylanase and 510 TGU kg−1 diet of endo-1,4-β-glucanase, with four replicates of 17 fish. Exogenous XB blend was top-sprayed in the control all-vegetable extruded diet containing 17.6 MJ kg−1 and 313.6 g kg−1 crude protein. Fish were stocked in 8–150 L aquaria in a recirculating aquaculture system with a water flow of 0.5 L s−1. The temperature was set at 28 °C and dissolved oxygen was maintained at 6.2 mg L−1 throughout the trial. Fish were hand-fed 12 times daily until apparent satiety for 90 days. Compared to the control group, fish in the XB group showed increased body weight gain (+29.7%), feed efficiency ratio (+25.4%), protein retention efficiency (+30.6%), energy retention efficiency (+41.6%), whole-body lipids (+10.7%), blood glucose (+37.8%), blood total triglycerides (+42.8%) and gut villus height (+22.1%). Analysis of the “core microbiota” revealed that fish in the XB group presented 2355 unique operational taxonomic units (OTUs) that were not shared with the control group. Additionally, fish in the XB group demonstrated an increased abundance of beneficial bacteria Bifidobacterium (+500%) and decreased abundance of potentially harmful bacteria Streptococcus (−98.04%), Faecalibacterium (−73.7%), and Escherichia-Shigella (−94.7%) in the gut digesta. Overall, XB can enhance the growth performance of pre-growout Nile tilapia by improving feed efficiency, gut morphology, and the abundance of beneficial gut microbiota.