Article ID Journal Published Year Pages File Type
5538995 Aquaculture 2018 50 Pages PDF
Abstract
The effects of increasing glycerol loading rates to create carbon to nitrogen (C/N) ratios of 0 (control), 10, 15 or 20 were investigated on the biofloc formation, biochemical composition and water quality, as well as the growth performance, feeding efficiencies, biochemical composition, trypsin/chymotrypsin enzyme activities, and liver glycogen of African catfish Clarias gariepinus after 6 weeks. Each treatment was triplicated and each replicate consisted of 25 juveniles (11.77 ± 0.01 g; mean ± SE). After six weeks, all fish were measured for growth, ten fish/replicate were used for additional analysis while ten fish/replicate were later challenged with the bacterial pathogen, Aeromonas hydrophila. Biofloc volume was significantly higher (P < 0.05) at C/N 20, but biofloc biomass was significantly higher (P < 0.05) at C/N 15. Dissolved oxygen was significantly lower (P < 0.05) at C/N 20 while total ammonia‑nitrogen was significantly higher (P < 0.05) in the control than the biofloc groups. Survival, growth, and feed utilization were similar among treatments (P > 0.05), but the input-output ratio significantly increased (P < 0.05) in the bioflocs groups. Fish muscle cholesterol, lipid peroxidation, serum triglyceride and serum cholesterol were all significantly lower (P < 0.05) in the biofloc groups, but liver glycogen was significantly higher (P < 0.05) in the C/N 15 treatment. Chymotrypsin activities were significantly higher (P < 0.05) in the biofloc groups, but trypsin was not different among the treatments. After challenging the catfish to A. hydrophila, survival was significantly higher (P < 0.05) in the C/N 15 and 20 groups, which was accompanied with less histopathological liver damage compared to those in the control or C/N 10 treatment. Overall, the results indicate that in a glycerol-based biofloc system, a C/N ratio of 15 led to the best balance of better water quality, nutritive value of C. gariepinus as well as their resistance to A. hydrophila.
Related Topics
Life Sciences Agricultural and Biological Sciences Aquatic Science
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