1. Dietary protein level and C/N ratio manipulation in zero-exchange culture of Litopenaeus vannamei: Evaluation of inorganic nitrogen control, biofloc composition and shrimp performance.
- Author
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Xu, Wu‐Jie and Pan, Lu‐Qing
- Subjects
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SHRIMPS , *FEED utilization efficiency , *ANIMAL nutrition , *LOW-protein diet , *WHITELEG shrimp , *WEIGHT gain - Abstract
A 30-day experiment was conducted to evaluate inorganic nitrogen control, biofloc composition and shrimp performance in zero-exchange culture tanks for juvenile L. vannamei offered a 35% (P35) or 25% (P25) crude protein feed, each feed supplemented with additional carbohydrate to increase the C/N ratio to 20:1 ( CN20) or 15:1 ( CN15). Sucrose was used as a carbohydrate to manipulate the two C/N ratios based on the carbon and nitrogen content of both the feeds and sucrose. The four treatments were referred to as: P35 + CN20, P35 + CN15, P25 + CN20 and P25 + CN15. Each treatment consisted of four replicate tanks (125 L), each stocked with 28 shrimp (equivalent to 224 shrimp m−3). Bioflocs formed and developed based on initial inoculation in all four treatments; and monitored water quality parameters were maintained within acceptable ranges for shrimp culture throughout the experiment. No significant effects ( P > 0.05) of dietary protein level, C/N ratio or their interaction were observed on biofloc development ( BFV, TSS and BFVI) and inorganic nitrogen ( TAN, NO2−-N and NO3−-N) concentrations. At the end of the experiment, proximate analysis of the bioflocs collected from the four treatments showed crude protein levels of 21.3% ~ 32.1%, crude lipid levels of 1.6% ~ 2.8% and ash levels of 43.4% ~ 61.4%. Extracellular protease and amylase activities of the bioflocs were 9.9 ~ 14.4 U g−1 TSS and 293.5 ~ 403.8 U g−1 TSS respectively. Biofloc composition and enzyme activity were both affected by dietary protein level ( P < 0.01) and C/N ratio ( P < 0.05). Survival, per cent weight gain and protein efficiency ratio of shrimp were not affected ( P > 0.05) by dietary protein level, C/N ratio or their interaction; however, the feed conversion ratios were significantly lower ( P < 0.05) in treatments with high dietary protein (P35) compared with those in treatments with low dietary protein (P25). The results from this study demonstrate that dietary protein level and C/N ratio manipulation can have important implications for water quality, biofloc composition and shrimp performance in intensive, zero-exchange biofloc-based culture systems. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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