Compensatory growth and body composition of juvenile Chinese sturgeon were investigated in indoor facilities at 19.0-22.3°Cafter food temporary deprivation under five feeding regimes: one group continuously fed and the other four groups were starved for 2, 4, 8 and 12 days, respectively followed by 16 days of re-feeding. During the starvation period, protein and lipid content of fish decreased slightly, while moisture and ash content of the starved groups became slightly higher compared to those of the control groups, with no significant differences. The hepatosomatic index (HSI) and the viscerosomatic index (VSI) for each test group (except s2) were significantly lower than that of the control groups. After re-feeding for 16 days, lipid content of fish increased significantly, while no significant differences were found in body biochemical composition, HSI and VSI comparing to the control groups. Final body weights and specific growth rates of s2, s4 were significantly higher than that of the control groups, showing over-compensatory growth; final body weights and specific growth rates of s8 were similar to the control groups, showing completely-compensatory growth; while the final body weights of s12 were lower than that of the control groups, with similar specific growth rates compared to the controls, showing partially compensatory growth. Food conversion efficiencies in groups S2 and s4 were significantly higher than that of the control groups; feeding rates of fish in group S8 and S12 were significantly higher than in the controls. We concluded that over-compensatory growth of S2 and S4 was acquired through raising food conversion rate, completely-compensatory growth of s8 and partially compensatory growth of s12 were acquired through increasing the feeding rate.

Five semi-purified diets were formulated to contain graded levels of dietary protein (340, 390, 440, 490 and 540 g/kg diet), and each diet was assigned to triplicate groups of eight juvenile Dabry's sturgeon for 50 days. Results showed that specific growth rate increased linearly with increasing dietary protein levels from 340 to 440 g/kg diet, then levelled off at higher protein levels. Higher dietary protein (440 and 540 g/kg) significantly increased the feed intake and feed efficiency ratio of fish compared to lower protein diets (340 to 490 g/kg diet) (p < .05). Fish fed a 440 g protein kg À1 diet had higher protein efficiency ratio and serum lysozyme activity than other treatments. Serum ammonia content and activities of liver aminotransferase were positively correlated with dietary protein levels. No significant difference (p > .05) among groups was observed in glycogen content. As dietary protein level increased, protein and ash content of fish dorsal muscle were greatly enhanced, whereas lipid content was significantly reduced (p < .05). Based on broken-line regression analysis of SGR against dietary protein levels, the optimum dietary protein level for maximal growth of juvenile Dabry's sturgeon is 446.68 g/kg diet.

To determine the effects of feeding rate and feeding frequency on growth performance, digestive enzymes activities, and intestine development of Megalobrama pellegrini in a replicated flow-through system, we conducted a 42day experiment. We designed three feeding rates (5%, 6.5%, and 8% body weight/day, BW/d) and two feeding frequencies (2 and 3 meals/day; m/d) in this experiment. Fish (0.57 ± 0.01 g) were distributed into 18 tanks with 70 individuals and fed with a commercial diet (33% crude protein, 4% total lipid). Results showed that the highest weight gain was found in the fish fed diet with 6.5% BW/day and 3 m/d, which was significantly higher in comparison with that of other feeding rate groups (5% BW/d and 6.5% BW/d) at both feeding frequency (2 and 3 m/d). Fish growth performance was significantly affected by the feeding rate but not by the feeding frequency. The significantly higher feed conversion ratio (FCR) was recorded at 8% BW/d with 3 m/d than other treatments. Furthermore, fish fed diet at 8% BW/d with 2 m/d had significantly high mortality during the middle of this trial. In contrast, we found that other fish groups' survival rates were higher (over 90%), and there were no significant differences among them. We saw a significantly lower whole-body crude protein, lipid, and intestinal digestive enzymes in fish fed at a ratio of 8% BW/d with 3 m/d compared with other treatments. Moreover, our findings revealed intestinal villi fusion and exfoliation in this group compared with other treatments. In conclusion, the Megalobrama pellegrini received a feeding rate of 6.5% BW/d, and a feeding frequency of 2 m/d may be the optimum feeding regime for raising Megalobrama pellegrini in a flow-through system.

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