The efficiency of indigenous isolates Bacillus sp. RCS1 and Bacillus cereus RCS3 on growth performance, blood biochemical indices and resistance against Vibrio harveyi in cobia fish (Rachycentron canadum) juveniles

Abstract

In this study, cobia (Rachycentron canadum) juveniles were utilised as an aquatic model to explore growth performance and immune indices after 70 days of feeding with supplementation of viable isolated microbes’ concentrations of 1 × 1010 and 1 × 1012 CFU/mL indigenous isolates Bacillus sp. RCS1 and Bacillus cereus strain RCS3, respectively. Regarding growth performance, fish provided with the indigenous isolates exhibited a significant (P 0.05) among the treatment and control groups tested; nonetheless, their mRNA expression exhibited variations in all trial groups. The present study showed significant differences (P < 0.05) among groups in the case of insulin-like growth factor 1, peroxisome proliferator-activated receptors. The improved antioxidant enzyme activities of catalase (CAT) and superoxide dismutase (SOD) digestive enzyme activities (amylase, trypsin, pepsin, lipase, and cellulose) may be linked to the enhanced resistance of fish against Vibrio harveyi infection. The enhanced activities of digestive enzymes in indigenous isolates treatments could be linked to the improved digestion and enhanced food absorption that ultimately helps enhance feed utilisation and growth performance. The results showed that indigenous isolates addition to a commercial diet, had the prospective to enhance cobia juveniles' growth and immune response regardless of their dosage.

Keywords

• Rachycentron canadum
• Indigenous strains
• Digestive enzyme activity
• Antioxidant enzyme activity