| In this paper, juvenile Nibea albiflora was chosen as the research object. A series of three experiments were conducted to study the optimum dietary protein, lipid and protein to lipid ratio of juvenile Nibea albiflora. The results obtained can be briefly summarized as the following three parts.1. The optimum dietary protein requirement of juvenile Nibea albiflora.Fishmeal, soybean meal and wheat gluten meal were used as main dietary protein source to formulate isoenergetic and isolipidic diets at six protein levels, which were 37.52%, 41.80%, 46.52%, 49.84%, 56.80% and 61.48%, Labeled as P1, P2, P3, P4, P5 and P6, respectively. A total of 360 Nibea albiflora with the average body weight of(17.84±0.34) g were randomly allocated into 6 groups with 3 replicates per group and 20 juvenile Nibea albiflora per replicate and they were reared in 500 L water-flowing glass fiber reinforced plastic buckets separately. An 8 week growth experiment was conducted under the condition of water temperature(27±2)? and salinity 28~29. The results showed that the rate of weight gain(WG), specific growth rate(SGR) and feed conversion rate(FCR) of P5 were slightly higher than P6(P>0.05) and significantly higher than the other groups(P<0.05). With the increasing of dietary protein levels, there were no significant changes in Hepatosomatic index(HSI), Viscera somatic index(VSI) and condition factor(CF) of juvenile Nibea albiflora(P>0.05). The differences of dietary protein levels had no influence on the contents of crude protein, crude lipid and ash in the body of juvenile Nibea albiflora(P>0.05). Dietary protein levels had significant influence on the content of Tau in muscle(P<0.05), but had little influence on the content of the other amino acids(P>0.05).The study found that the intestinal protease activity of juvenile Nibea albiflora increased at first and then keep stable with the increasing of dietary protein level(P<0.05). The dietary protein level had no significant influence on the activities of intestinal amylase, lipase as well as protease, amylase, lipase in the liver(P>0.05). The optimal dietary protein requirement, estimated by two slope broken-line model based on specific growth rate(SGR) against dietary protein levels was 55.39% of the dry matter for juvenile Nibea albiflora.2. The optimum dietary lipid requirement of juvenile Nibea albiflora.Fish oil and soybean lecithin were used as main dietary lipid source to formulate isonitrogenous diets at six lipid levels, which were 5.2%, 7.0%, 9.4%, 11.1%, 12.9% and 15.3%, labeled as L1, L2, L3, L4, L5 and L6, respectively. A total of 360 Nibea albiflora with the average body weight of(17.70±0.20) g were randomly allocated into 6 groups with 3 replicates per group and 20 juvenile Nibea albiflora per replicate and they were reared in 500 L water-flowing glass fiber reinforced plastic buckets separately. An 8 week growth experiment was conducted under the condition of water temperature(27±2)? and salinity 28~29. The results showed that the weight gain(WG) and specific growth rate(SGR) of L5 and L6 were significantly higher than those of L1(P<0.05). The feed conversion rate(FCR) of L5 was significantly lower compared with the values obtained from the other groups(P<0.05). The protein efficiency ratio(PER) increased first and then decreased, but the difference was not significant(P>0.05). The content of lipid in whole body and muscle increased significantly with the increasing of dietary lipid levels(P<0.05). Hepatosomatic index(HSI) of L3 was significantly higher than that of animals L6(P<0.05). Viscera somatic index(VSI) of L1 was the highest, which significantly higher than those of L5 and L6(P<0.05). There were no significant differences in condition factor(CF) among different treatments(P>0.05). The content of EPA, DPA, DHA, ?n-3 and ?n-3 HUFA increased with the increasing of dietary lipid levels(P<0.05). At the same time, the content of C18:1n9t, ?MUFA decreased significantly(P< 0.05). Intestinal lipase activity increased first and then decreased with the increasing of dietary lipid level(P<0.05).The superoxide dismutase(SOD) activity in liver increased significantly(P<0.05) and then maintained at a steady state as the dietary lipid level increased and the maximum value appeared in L5. The content of malondialdehyde(MDA) in liver increased significantly with the increasing of dietary lipid level(P<0.05). Broken-line analysis based on specific growth rate(SGR) indicated that the optimal dietary lipid level for juvenile Nibea albiflora was 11.83%.3.The optimum dietary protein to lipid ratio of juvenile Nibea albiflora.Fishmeal, soybean meal and corn gluten meal were chosen as the main dietary protein source, fish oil, soybean oil and soybean lecithin were chosen as lipid source. Nine practical diets were formulated in the study, which contain three protein levels(40%,47%,54%) and there were three lipid levels(5%,9%, and 13%) at each protein level, labeled as P40L5, P40L9, P40L13, P47L5, P47L9, P47L13, P54L5, P54L9 and P54L13,respectively.A total of 540 Nibea albiflora with the average body weight of(11.76±0.20)g were randomly allocated into 9 groups with 3 replicates per group and 20 juvenile Nibea albiflora per replicate and they were reared in 500 L water-flowing glass fiber reinforced plastic buckets separately. The results showed that no interaction between dietary protein and lipid existed for growth performance(P>0.05). Weight gain(WG) and specific growth rate(SGR) increased significantly with the increasing of dietary protein and lipid level(P<0.05). Feed conversion rate(FCR) decreased significantly with the increasing of dietary protein and lipid level(P<0.05). Protein efficiency ratio(PER) increased significantly with the increasing of dietary lipid level(P<0.05). With the increasing of dietary lipid level, the content of lipid in whole body and muscle increased significantly(P<0.05). Dietary lipid level significantly affected Hepatosomatic index(HSI)(P<0.05)but had no significant effects on Viscera somatic index(VSI) and condition factor(CF)(P>0.05). Different dietary protein levels affected the content of Cys significantly(P<0.05), but had no significant effects on the other amino acids(P>0.05). The content of EPA increased significantly with the increasing of dietary lipid levels(P<0.05). The content of SFA increased significantly with the increasing of dietary protein levels(P<0.05). The content of MUFA increased significantly with the increasing of dietary protein levels(P<0.05), but decreased significantly with the increasing of dietary lipid levels(P<0.05).The activity of intestinal protease increased significantly with the increasing of dietary protein levels(P<0.05). The activity of intestinal lipase increased significantly with the increasing of dietary lipid levels(P<0.05). With the the increasing of dietary protein level, the activity SOD increased significantly(P<0.05) but the content of MDA in liver decreased significantly(P<0.05). With the the increasing of dietary lipid level, the activity of SOD and the content of MDA in liver increased significantly(P<0.05). The group of P54L13 had the best growth performance and the lowest feed conversion rate(FCR), at this time, the content of crude protein in dietary was 54.55%, the crude lipid content in daitary was 13.83%, and then the optimum protein to lipid ratio of juvenile Nibea albiflora can be preliminarily identified as 54.55%:13.83%, namely 3.94:1. |
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