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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(s) -
Xu WuJie,
Pan LuQing
Publication year - 2014
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.12126
Subject(s) - litopenaeus , shrimp , biology , sucrose , zoology , nitrogen , carbohydrate , food science , amylase , composition (language) , penaeidae , decapoda , fishery , biochemistry , crustacean , enzyme , chemistry , linguistics , organic chemistry , philosophy
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 ( CN 20) or 15:1 ( CN 15). 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 + CN 20, P35 + CN 15, P25 + CN 20 and P25 + CN 15. 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 , NO 2 − ‐N and NO 3 − ‐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.