DEVELOPMENT OF AUTOCHTHONOUS PROBIOTIC CANDIDATES FOR TILAPIA AQUACULTURE

This programme of work sought to develop autochthonous probiotic solutions for tilapia aquaculture. Initial work began with the isolation of isolate 34 bacterial cultures from the tilapia intestine, which were tested for probiotic potential in vitro. Fifteen isolates displayed positive probiotic properties in in vitro assays. The selection of high potential probiotic candidates was based on multi-parameter properties using the Z−score method, which ranked isolates identified as Bacillus sp. CHP02 (Z score = 1.48), Bacillus sp. RP01 (1.14) and Bacillus sp. RP00 (1.09) as having the greatest potential. These isolates, along with Enterobacter sp. NP02 (0.50), were then assessed for their efficacy as probiotic candidates in vivo. Six experimental groups: T1: (Bacillus sp. CHP02 + a commercial feed), T2 (Bacillus sp. RP01 + a commercial feed), T3 (Bacillus sp. RP00 + a commercial feed), T4 (Enterobacter sp. NP02 + a commercial feed), T5 (P. acidilactici + a commercial feed) and T6 (only + a commercial feed) were designed for evaluation in both fry and on-growing stages of tilapia. Bacillus sp. RP01 application to feeds induced positive effects on tilapia larvae including improved body weight, total weight gain, average daily growth, specific growth rate and resistance to A. hydrophila challenge. However, these beneficial effects were not observed when applied in on-growing sized tilapia. The results suggest that the Z-score method could be used to select high potential of autochthonous probiotics for fry, but the applicability in the current research programme was less robust at later life stages. It is hypothesised that different probiotic strains may be required for application during different life stages, which may reflect the different physiologies of tilapia, and their likely differing microbiomes, at different life histories. Further research is required to select probiotics by using re-isolation and both in vitro and in vivo trials across the whole tilapia production cycle.King Mongkut's Institute of Technology Ladkrabang's Foundation, Thailan

Combined effects of exogenous enzymes and probiotic on Nile tilapia (Oreochromis niloticus) growth, intestinal morphology and microbiome

A study was carried out to investigate the combined effect of exogenous enzymes and probiotic supplementation on tilapia growth, intestinal morphology and microbiome composition. Tilapia (34.56 ± 0.05 g) were fed one of four diets (35% protein, 5% lipid); one of which was a control and the remaining three diets were supplemented with either enzymes (containing phytase, protease and xylanase), probiotic (containing Bacillus subtilis, Bacillus licheniformis and Bacillus pumilus) or enz-pro (the combination of the enzymes and probiotic). Tilapia fed diet supplemented with enz-pro performed better (P < 0.05) than tilapia fed the control and probiotic supplemented diets in terms of final body weight (FBW), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER). The dietary treatments did not affect somatic indices. The serum lysozyme activity was significantly higher (P < 0.05) in tilapia fed the probiotic supplemented diet than of those fed the remaining experimental diets. The intestinal perimeter ratio was higher (P < 0.05) in tilapia fed enz-pro supplemented diet when compared to those fed with the control and probiotic supplemented diets. Goblet cells abundance, microvilli diameter and total enterocyte absorptive surface was higher (P < 0.05) in tilapia fed diet supplemented with enz-pro than those fed the control diet. High-throughput sequencing revealed that majority of reads derived from the tilapia digesta belonged to members of Fusobacteria (predominantly Cetobacterium) distantly followed by Proteobacteria and Firmicutes. The alpha and beta diversities did not differ among dietary treatments indicating that the overall microbial community was not modified to a large extent by dietary treatment. In conclusion, supplementation of the diet with a combination of enzymes and probiotic is capable of improving tilapia growth and intestinal morphology without deleterious effect on the intestinal microbial composition