| With the development of aquaculture industry in the world, the demand of aquatic feed is becoming increasingly huge. Due to the price of fish meal is rising these years, the phenomenon of fish meal shortage is widely attention. Searching suitable protein resource to all or part replace fish meal of aquatic feed is widely reported. As the most expensive component in fish feeds, the effect of non-protein energy sources were conducted which is a process known as ‘‘protein sparing”. Therefore, dietary protein to energy(P/E) ratio is an important index in fish feed formulation and suitable P/E ratio plays an important role in sustainable development of aquaculture. Comparative research on apparent digestibility of twelve feed ingredients for Cirrhinus mrigalaApparent digestibility coefficients of dry matter, crude protein, crude lipid, gross energy, P, Ca, Mg, Zn, Cu, Fe and Mn in domestic fish meal(DFM), white fish meal(WFM), peanut meal(PNM), DDGS, chicken meal(CM), rice bran(RB), cottonseed meal(CSM), rapeseed meal(RSM), soybean meal(SBM), corn gluten meal(CGM), corn DDGS(CDDGS) and feather meal(FTM) were determined for juvenile Cirrhinus mrigala(3.88 ± 0.06 g). Apparent digestibility coefficients were determined using a reference diet with 0.1% Y2O3. Test diets contained 70% reference diet and 30% of the feed ingredient were evaluated. The results showed that apparent digestibility of dry matter, crude protein, crude lipid, gross energy, P, Ca, Mg, Zn, Cu, Fe and Mn of twelve ingredients were among 24.93%-85.68%, 50.02%-97.40%, 51.89%-94.02%, 39.18%-96.39%, 9.72%-87.37%, 3.47%-25.92%, 26.11%-88.25%, 12.63%-66.35%, 41.33%-104.86%, 10.69%-91.84% and 4.42%-85.49%, respectively. DFM and WFM had the highest apparent digestibility of dry matter, crude protein and gross energy. In other ingredients except for fish meal, PNM, SBM and CGM had the highest apparent digestibility of dry matter; PNM had the highest apparent digestibility of crude protein; RB and PNM showed the highest apparent digestibility of crude lipid; PNM and CM had the highest apparent digestibility of gross energy; DDGS showed the lowest apparent digestibility of dry matter, crude protein, crude lipid, gross energy. As for apparent digestibility coefficients of minerals, FTM had the highest apparent digestibility of P, Cu, Fe and Mn; RB had the highest apparent digestibility of Zn; WFM, SBM and FTM had the highest apparent digestibility of Ca; SBM, FTM and CDDGS had the highest apparent digestibility of Mg. CM had the lowest apparent digestibility of P, Ca, Mg and Fe; PNM and CSM had the lowest apparent digestibility of Zn; RSM and DDGS showed the lowest apparent digestibility of Cu and Mn, respectively. Therefore, PNM, SBM, CGM were good protein sources for juvenile C. mrigala which might be used in formula feed to replace fish meal; RB could be used as superior energy source; FTM could be considered as the potential source of minerals in formula feed. Effects of dietary protein and energy levels on growth performance, feed utilization and body composition of juvenile C. mrigalaFive practical extruded diets were formulated to investigate the effect of graded levels of P/E ratios(17.78 mg/kJ, 19.37 mg/kJ, 21.70 mg/kJ, 24.06 mg/kJ, 26.25 mg/kJ) associated with 25% to 41% protein level on growth performance, feed utilization and body composition of juvenile C. mrigala 300 fish(6.05 ± 0.06 g) were randomly distributed into five treatment groups(E1, E2, E3, E4, E5, respectivly) each with three replicates. The results showed that fish fed the diet E3 had the highest weight gain(WG) and specific growth ratio(SGR), and were significant higher than other groups(P < 0.05). Feed coefficient ratio(FCR) in fish fed with diet E3 was significant lower than that in E1, E2 and E5(P < 0.05), but showed no significant difference with that in E4(P > 0.05). The protein retention efficiency(PRE) in fish fed the diet E3 and E4 was significant higher than that in E1 and E5(P < 0.05), but showed no significant difference with that in E2(P > 0.05). No significant differences were found of protein efficiency ratio(PER) in fish fed with the diets E1, E2 and E3(P > 0.05), while fish fed with the diets E4 and E5 showed significantly lower protein efficiency ratio(PER) than E1, E2 and E3(P < 0.05). With the increase of dietary P/E ratios, the crude protein of whole body first increased then decreased, on the contrary, the moisture first decreased then increased. By the analysis of quadratic curve regression equation, the weight gain(WG) obtained the highest value as the dietary P/E ratio was 22.35 mg/kJ, the feed coefficient ratio(FCR) showed the lowest value as the dietary P/E ratios was 22.37 mg/kJ. These results suggest that the optimal dietary P/E ratio in diets for juvenile C. mrigala was ranged from 22.35 mg/kJ to 22.37 mg/kJ, associated with 34.50% to 34.57% protein level. |
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