Mohammad Hossien khanjani

The effect of different carbon sources in the biofloc system on growth performance, body biochemical compositions, digestive and hepatic enzymes of Nile tilapia was investigated in this research. Oreochromis niloticus fingerlings with average weight of 1.57±0.12 g were cultured for 37 days in fiberglass tanks (130 L), at a density of one fish per liter. The experiment was designed in five treatments including one control group and four biofloc treatments by adding different carbon sources: molasses (BFTM) and starch (BFTS) (complex carbon sources), barley flour (BFTB) and corn (BFTC) (simple carbon sources). Results showed the lowest dissolved oxygen (5.45 mg. L-1), pH (7.25) and feed conversion rate (0.99) in BFTS treatment (p<0.05), while the latter showed the highest protein efficiency ratio (2.91) and survival rate (98.2%). There were no significant differences in growth performance among various treatments (p<0.05).Somatic indices improved in biofloc treatments compared to the control group. Bioflocs formed in different carbon sources showed different nutritional value (p<0.05) which affected the quality of carcass analysis. The highest amount of amylase (95.86 U/mg protein) and protease (17.77 U/mg protein) activities were obtained in BFTB treatment and the lowest amount of hepatic enzymes activity was observed in the BFTS treatment (p<0.05). Generally, the present study showed that cultured tilapia using in situ biofloc produced by different carbon sources can promote FCR, survival, body composition, digestive and hepatic enzymes compared to the control group. Improved digestive activities are more noticeable in complex carbon sources and hepatic enzymes activities are stronger in simple carbon sources.