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Effect of the C/N ratio on inorganic nitrogen control and the growth and physiological parameters of tilapia s fingerlings, Oreochromis niloticu reared in biofloc systems
Author(s) -
Liu Gang,
Zhu Songming,
Liu Dezhao,
Ye Zhangying
Publication year - 2018
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.13702
Subject(s) - biology , oreochromis , tilapia , alkaline phosphatase , zoology , lysozyme , superoxide dismutase , malondialdehyde , food science , biochemistry , enzyme , antioxidant , fishery , fish <actinopterygii>
The objective of this study was to document the effects of different C/N ratios on inorganic nitrogen control and the growth and health of tilapia ( Oreochromis niloticus ) fingerlings reared in biofloc systems. The fish (0.50 ± 0.02 g) were randomly assigned to the control group (clear water) or to one of three biofloc groups (added glucose) with a C/N ratio of 10, 15, or 20 ( CN ‐10, CN ‐15, or CN ‐20, respectively). All four groups were cultured for 120 days. The inorganic nitrogen dynamics showed that heterotrophic and autotrophic bacteria existed in the low C/N ratio group, and heterotrophic bacteria dominated the high C/N ratio group. In addition, growth was significantly better in the CN ‐10 and CN ‐15 groups (15.67 ± 0.78 g and 14.75 ± 0.54 g, respectively) compared to the CN ‐20 (13.04 ± 0.94 g) and control (13.04 ± 0.46 g) groups ( p < .05). Activities of the digestive enzymes lipase and trypsin were significantly higher in the CN ‐10 and CN ‐15 groups than in the control group ( p < .05). In addition, activities of lysozyme, alkaline phosphatase, superoxide dismutase, glutathione and malondialdehyde were significantly higher in the CN ‐10 and CN ‐15 groups than in the control group ( p < .05). Finally, the concentrations of glucose and cortisol in the biofloc systems were significantly lower than those in the control group ( p < .05). However, the concentrations of triglyceride, aspartate transaminase and alanine aminotransferase did not differ significantly among the four groups ( p > .05). At the end of the trial, an acute crowding and hypoxia stress test performed for 3 days showed that the CN ‐10 and CN ‐15 groups had the best survival.