Effects of diets containing Lactococcus lactis and Bacillus subtilis on growth indices and hepatic enzymes of tiger oscar (Astronotus ocellatus)

Tiger oscar (Astronotus ocellatus) is a favorite for aquarium fish enthusiasts due to its beauty and compatibility. The study was conducted to evaluate the effects of Lactococcus lactis and Bacillus subtilis on growth efficacy and hepatic enzymes of oscar by selecting 300 juveniles with a mean weight of 8.96±0.03g and length of 8.23±0.02cm. During 70 days fishes fed by diets contained L. lactis and B. subtilis in 9 single and combined treatments groups with the number 1010CFU/g bacteria in treatments which included 150, 300, and 450mg/kg of L. lactis (LL150, LL300, and LL450), 150, 300, and 450 mg/kg of B. subtilis (BS150, BS300, and BS450), 150, 300, and 450 mg/kg of an equal mixture of L. lactis and B. subtilis (MIX150, MIX300, and MIX450) and control group. Finally, their growth indices and hepatic enzymes were assessed. Results showed that applying both bacteria in the feeding of oscar fish has significantly improved the growth indices. Also, adding bacteria in the diet led to increased weight gain (WG), body weight index (BWI), average daily growth (ADG), Specific growth rate (SGR), final biomass and protein efficiency ratio (PER) compared to control (p < 0.05). All single and combined treatments compared to control had the most reduction of FCR which was statistically significant (p < 0.05). Also, the highest statistically significant difference between hepatic enzymes, alanine aminotransferase and aspartate aminotransferase was measured with control in treatment 3 (LL450) and alkaline phosphatase in treatment 9 (MIX450) (p < 0.05). The addition of these bacteria individually or in combination had a positive effect on growth indices and liver enzymes.