Application of probiotic microcapsules Bacillus cereus BR2 with different doses for the prevention of Aeromonas hydrophila NFC1 infection in catfish Clarias sp.

This study aims to analyze the administration of microencapsulated probiotic Bacillus cereus BR2 through feed with different doses on the survival, immune response, and digestive enzyme activity of catfish Clarias sp. infected with Aeromonas hydrophila NFC1. The research design used consisted of five treatments and three replications, namely (K-) feeding without the supplementation of probiotics; fish injected with Phosphate-buffered saline (PBS) solution; (K+) feeding without the supplementation of probiotics, fish injected with A. hydrophila NFC1 cell suspension (106 CFU mL-1); (P1) feeding with supplementation of B. cereus BR2 microcapsules at a dose of 0.5% (w/w); (P2) feeding with the supplementation of B. cereus BR2 microcapsules at a dose of 1% (w/w; (P3) feeding with the supplementation of B. cereus BR2 microcapsules at a dose of 2% (w/w). all treatments of P1, P2, and P3 were intramuscularly injected with A. hydrophila NFC1 cell suspension. Catfish fingerlings in average body weight approximately of 3.73 ± 0.22 g were reared in tanks filled with 30 liters of water, and at a density of 15 fish in each container. A feed supplementation trial was performed for 40 days with feeding times three times a day; based on fish biomass feeding rate. Fish rearing was continued after the challenge test with A. hydrophila NFC1 for 10 days. The results showed that the application of supplemented feed containing B. cereus BR2 probiotic microcapsules increased the survival rate, immune response, and digestive enzyme activity of catfish Clarias sp. which was infected with A. hydrophila NFC1, with the best results at 2% microcapsule supplementation.