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A 75-day experiment was conducted with 6 different feeding regimes to evaluate compensatory responses in growth, physiological state, and muscle biochemical composition of juvenile Procambarus clarkii (1.37 ± 0.03 g). P. clarkii were deprived of feed for 0 day (control group), 2 (treatment 2), 4 (treatment 3), 8 (treatment 4), 16 (treatment 5), and 24 days (treatment 6) before being fed daily until day 75. Each feeding regime was tested in 10 replicate tanks with four crayfish in each tank. The growth (survival, SGRw, FCR, feeding rate, moulting frequency, HSI, PI, growth trajectory analysed using schnute model), digestive enzymes (trypsin and lipase), energy reserves and metabolites (alkaline phosphatase, total protein, total cholesterol, triglyceride, aspartate transaminase, and pyruvate kinase), antioxidant enzymes (superoxide dismutase, catalase, and malondialdehyde), and muscle biochemical composition (crude protein, crude lipid, ash, and moisture) were evaluated every 25 days. Results showed that P. clarkii in treatments 3 and 4 had similar growth as those in the control group but higher feeding rates at the end of the experiment, indicating that full compensatory growth occurred, while crayfish in treatments 5 and 6 only showed partial compensation. No compensation was observed in treatment 2. Furthermore, P. clarkii in treatment 4 had better feed utilisation efficiency, with a significantly lower FCR than those in other groups. The feed-deprivation period significantly influenced the physiological state of P. clarkii, with significantly lower values of variables of energy reserves and metabolites observed in treatments 5 and 6, except for alkaline phosphatase. Furthermore, P. clarkii in treatment 6 had significantly lower catalase activity but higher trypsin activity and malondialdehyde content than those in other groups. Muscle biochemical composition analysis revealed that P. clarkii in treatments 5 and 6 had significantly lower crude protein and lipid contents than other groups. The physiological state and muscle biochemical composition of crayfish varied over time (days 25, 50, and 75), with markedly increased activities or contents of total cholesterol, triglycerides, aspartate transaminase, catalase, crude protein and crude lipid observed in all treatments except the control group at the end of the experiment. Collectively, these results demonstrate that long-term feed deprivation (16 and 24 days) could only elicit partial compensation in growth, physiological state, and muscle biochemical composition of P. clarkii, while feed deprivation for 4 and 8 days followed by refeeding until day 75 could effectively trigger full compensation, particularly with respect to improve feed utilisation efficiency. |
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