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

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.

Impact of early-life rearing history on gut microbiome succession and performance of Nile tilapia

“…Statistically significant ( P < 0.05) correlations were further visualised with Gephi software ( http://gephi.github.io/ ). In the network, the following parameters were calculated: (A) average degree, which is the frequency of all the nodes’ degrees; (B) cluster coefficient, which is the ratio between existing and possible edges between a node’s neighbours; (C) density, which is the ratio of the number of total edges to the number of possible edges between all the nodes; (D) path length, which is the average shortest path of all possible nodes; and € modularity, which is the strength of division of a network into modules, in order to assess the network topology [ 42 – 44 ].…”

“…The treatment effect on gut microbiome composition at ASV level was analysed by PERMANOVA, using Primer. Pearson correlations between the gut ASV matrix and fish performance predictors (body weight, body composition, digestibility, as well as nitrogen and energy retention efficiency) at 105 dof, were tested by distance-based linear modelling (DistLM) in Primer [ 42 ]. The similarity of gut microbiome between the two early life rearing systems-originated fish at each sampling time was calculated by similarity percentage (SIMPER) analysis using PAST software.…”

Designing Biological Micro-Sensors with Chiral Nematic Liquid Crystal Droplets

“…The capability to sense amphiphiles in vivo within the zebrafish additionally shows great promise in being able to rapidly detect and sense the presence of biologically relevant markers, such as amphiphilic short-chained fatty acids, which typically require complex set-ups or sophisticated equipment to detect 38 . Other applications for in vivo sensing in fish include detecting how well feed is uptaken and metabolized, enabling for further optimization of animal husbandry 37 . We could envision incorporating CLC droplets into the feed, either for imaging within the animal or for post-analysis after passing through the digestive tract; such an ingestion-and-retrieval strategy of microsensors to detect and profile the interacting bioamphiphiles may give the opportunity to gain information about the health of animals much more rapidly and potentially capable of used by lay technicians without the necessity of specialized equipment.…”

“…However, the signal does become cleaner and more distinctive with polarizers (Figure 4(d)), as the polarizers cut out any reflection from non-birefringent materials. Thus, we can conclude that amphiphilic molecules present in the gut, likely the metabolic byproducts of the gut microbiota 37,38 , are responsible for switching the droplet alignment. The aqueous medium in which the fish were swimming did not switch the droplet alignment.…”

In-Situ Biofloc Affects the Core Prokaryotes Community Composition in Gut and Enhances Growth of Nile Tilapia (Oreochromis niloticus)

“…4). Species belong to Cetobacterium and Peptostreptococcaceae were widely detected in the gut of Nile tilapia with high abundance [9,18,[49][50][51][52]. The dietary treatment of in-situ or ex-situ biofloc changed the relative abundance of core gut microbiota of tilapia (Table 2).…”