Recirculating aquaculture systems (RAS) offers several advantages, such as increased production and water conservation, but they can lead to elevated nitrogenous waste levels due to their intensive nature. This 60-day feeding trial investigated the effects of six hetero-nitrogenous and hetero-caloric diets on genetically improved farmed tilapia (GIFT) fingerlings reared in RAS. Six diets, with decreasing crude protein from 40% to 30% and increasing lipid levels from 7% to 12% were formulated and designated as: T1 (40% CP, 7% lipid), T2 (38% CP, 8% lipid), T3 (36% CP, 9% lipid), T4 (34% CP, 10% lipid), T5 (32% CP, 11% lipid), and T6: 30% CP, 12% lipid). GIFT fingerlings (initial weight 5.05 ± 0.03 g) were stocked evenly into eighteen RAS tanks, maintaining stocking density of 6000 g/m3. Results showed a significant (p 0.05) among the different treatment groups. The gill superoxide dismutase (SOD) and catalase (CAT) activities, indicators of oxidative stress, were elevated (p < 0.05) in T5 and T6, while liver CAT activity, crucial for hydrogen peroxide detoxification, also increased significantly (p < 0.05). The T4 group (34% CP, 10% lipid) exhibited significantly (p < 0.05) higher specific growth rate and lower NH3-N, NO2-N, and NO3-N levels compared to other groups. Therefore, a diet of 34% CP and 10% lipid is recommended for GIFT fingerlings in RAS to promote growth and to minimise nitrogenous waste.
Mannur et al. (Thu,) studied this question.
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