African catfish (Clarias gariepinus) and lemon fin barb hybrid (LFBH) (Hypsibarbus wetmorei ♂ × Barbodes gonionotus ♀) were cultured in either a biofloc technology (BFT) system or an individual recirculating aquaculture system (RAS) and their survival, growth, feeding efficiencies and biochemical composition were then compared after 8 weeks. LFBH and African catfish were chosen based on their different feeding habits. In the BFT treatments, glycerol was added to create a carbon to nitrogen ratio of 15, while the RAS system consisted of a fine mesh mechanical and biological filter. Each of the four treatments was triplicated, with each replicate consisting of 20 African catfish (0.98 ± 0.05 g) or LFBH (1.77 ± 0.02 g). Water quality and biofloc formation were examined weekly while the biofloc proximate composition was measured in weeks 5 and 8. During weeks 6, 7 and 8 the total viable bacterial colony forming units (CFU) were quantified. Regardless of species, biofloc formation was similar but the crude protein, lipid and ash significantly decreased from week 5 to week 8. However, biofloc crude protein and ash were significantly higher in the LFBH treatment. Total viable CFU were significantly higher (P < 0.05) in BFT compared to RAS, with LFBH having significantly more (P < 0.05) than African catfish. The proximate composition of the fish were unaffected by either system. Implementing BFT significantly (P < 0.05) improved both African catfish and LFBH growth, but this improvement was substantially higher for LFBH (41.6%) than for African catfish (7.6%). This may be due to a better ability of LFBH to consume smaller particles. Preliminary results also indicate that the nutritional composition of bioflocs could be influenced by biofloc age, which could have implications to solids management.
The effects of Bacillus cereus strain BP‐MBRG/1b (probiotic), 0.4% fructooligosaccharides (prebiotic) and its combination synbiotic dietary supplementations were evaluated in M. rosenbergii juveniles through feeding trials. After 28 days of feeding, the results showed that the probiotic fed juveniles had the highest specific growth rate (SGR) (1.00 ± 0.02%/day) compared with the prebiotic (0.42 ± 0.08%/day) and synbiotic (0.54 ± 0.08%/day) treatments. The prawns were then challenged with pathogenic Aeromonas hydrophila strain AH‐1N via static immersion. No significant differences were observed in terms of mortalities for the first challenge nor in the second challenge for all the treatments. Histological observations of the prawn hepatopancreas in all the treatment groups demonstrated necrosis and sloughing of the cells. Overall, the present result suggested that B. cereus strain BP‐MBRG/1b demonstrated enhancement of growth performance in M. rosenbergii compared with prebiotic and synbiotic treatments. However, further investigation is required to study the optimal dosage of the synbiotic treatment (probiotic B. cereus strain BP‐MBRG/1b and prebiotic fructooligosaccharides) against A. hydrophila challenged M. rosenbergii.
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