Exogenous enzymes and probiotics alter digestion kinetics, volatile fatty acid content and microbial interactions in the gut of Nile tilapia

Roel M Maas,Yale Deng,Yueming Dersjant-Li,Jules Petit,Johan W Schrama,Marc C J Verdegem,Fotini Kokou

doi:10.1038/s41598-021-87408-3

Abstract

Sustainable aquafeed production requires fishmeal replacement, leading to an increasing use of plant-derived ingredients. As a consequence, higher levels of antinutritional substances, such as non-starch polysaccharides and phytate, are present in aquafeeds, with negative effects on fish performance, nutrient digestibility and overall gut health. To alleviate these negative effects, providing exogenous digestive enzymes and/or probiotics can be an effective solution. In this study, we tested the effect of dietary supplementation of enzymes (phytase and xylanase) and probiotics (three strains of Bacillus amyloliquefaciens) on nutrient digestion kinetics and volatile fatty acid content along the gut, and the distal gut microbiome diversity in Nile tilapia. Chyme volatile fatty content was increased with probiotic supplementation in the proximal gut, while lactate content, measured for the first time in vivo in fish, decreased with enzymes along the gut. Enzyme supplementation enhanced crude protein, Ca and P digestibility in proximal and middle gut. Enzymes and probiotics supplementation enhanced microbial interactions as shown by network analysis, while increased the abundance of lactic acid bacteria and Bacillus species. Such results suggest that supplementation with exogenous enzymes and probiotics increases nutrient availability, while at the same time benefits gut health and contributes to a more stable microbiome environment.

Highlights

Sustainable aquafeed production requires fishmeal replacement, leading to an increasing use of plantderived ingredients
The chyme volatile fatty acids (VFA) composition along the gastrointestinal tract (GIT) of fish fed with the four different diets was measured (Fig. 1), showing a dominance of acetic acid (86– 88%), followed by propionic acid (10–12%) (Fig. 1a). (Iso) butyric and valeric acid acids were detected in lower concentrations(Table 1)
A different trend was observed by the probiotics showing an increase in the lactic acid concentration after the stomach; we did not find a significant difference with the control (P > 0.1)

Summary

Introduction

Sustainable aquafeed production requires fishmeal replacement, leading to an increasing use of plantderived ingredients. Higher levels of antinutritional substances, such as non-starch polysaccharides and phytate, are present in aquafeeds, with negative effects on fish performance, nutrient digestibility and overall gut health To alleviate these negative effects, providing exogenous digestive enzymes and/or probiotics can be an effective solution. We tested the effect of dietary supplementation of enzymes (phytase and xylanase) and probiotics (three strains of Bacillus amyloliquefaciens) on nutrient digestion kinetics and volatile fatty acid content along the gut, and the distal gut microbiome diversity in Nile tilapia. Several studies in white leg shrimp, gilthead sea bream and Nile tilapia revealed that Bacillus species could change the bacterial diversity and proportional composition of bacterial phyla in the gut[27,28]

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Discussion

Conclusion