Study On Nutrient Physiology Of Chromium And Manganese For Juvenile Litopenaeus Vannamei

The present study were conducted to determine the optimum dietary requirement of chromium and manganese for Litopenaeus vannamei with chromium trichloride(Cr Cl3),chromium picolinate(Cr-Pic), methionine chromium(Cr-Met), as chromium sources;manganese sulfate(Mn-S), methionine manganese(Mn-Met), as manganese sources, and to investigate the effects of different Cr and Mn sources and levels, respectively on the growth performence, serum biochemical indices, non-specific immune enzymes activities and elements content in tissue of Litopenaeus vannamei. The results are presented as follows:1. This experiment was conducted to study the effects of dietary chromium sources and supplemental levels on growth performance, serum biochemical indices, non-specific immune enzyme activities, Cr concents of tissue and flavour amino acid contents of juvenile Litopenaeus vannamei. Sixteen isonitrogenous and isoenergetic diets were formulated by using two-factor experimental design with three chromium sources(Cr Cl3,Cr-Pic and Cr-Met, respectively) and different chromium supplemental levels(0, 0.3, 0.6,0.9, 1.2 and 2.0 mg/kg, respectively). A total of 1 920 juvenile Litopenaeus vannamei with an initial body weight of(0.895±0.001 g) were randomly distributed into 16 groups with 3replicates per group and 40 shrimps per replicate. The experiment lasted for 8 weeks. The results showed that final body weight(FBW), weight gain rate(WGR), feed conversion rate(FCR) and protein efficiency ratio(PER) of shrimps were significantly affected by chromium sources, supplemental levels and the interaction of chromium sources and supplemental levels(P<0.05). The FBW and WGR in groups supplemented with 0.3 mg/kg to 2.0 mg/kg chromium were significantly higher than the control group(P<0.05), and the Cr-Met group supplemented with 0.9 mg/kg chromium had the highest FBW and WGR.The groups of Cr Cl3 and Cr-Pic supplemented with 0.9 mg/kg chromium had the lowest FCR, but showed no significant differences compared with 1.2 mg/kg group(P>0.05). The highest PER of three chromium sources were founded in the groups supplemented with 0.9mg/kg chromium, but showed no significant differences compared with 1.2 mg/kg group(P>0.05). Chromium source, supplemental level and the interaction of chromium source and supplemental level had significant effects on the crude lipid and crude ash contents in whole body(P<0.05), but had no significant effects on the moisture, crude protein content in whole body(P>0.05). Serum total protein(TP), glucose, total cholesterol(CHOL) andtotal triglyceride(TG) contents were significantly affected by chromium source,supplemental level and the interaction of chromium source and supplemental level,respectively(P<0.05). The highest TP content and lowest glucose content were found in the Cr-Met group supplemented with 0.9 mg/kg chromium. The activities of phenoloxidase(PO), alkaline phosphatase(AKP), acid phosphatase(ACP) and the total superoxide dismutase(T-SOD) in serum were significantly affected by chromium source,supplemental level and the interaction of chromium sources and supplemental levels(P<0.05). The highest PO and T-SOD activities were found in the Cr-Met group supplemented with 0.9 mg/kg chromium. Chromium source, supplemental level and the interaction of chromium source and supplemental level had significant effects on the Cr contents in the hepatopancreas(P<0.05), but had no significant effects on the Cr contents in the muscle(P>0.05). The highest Cr concents were found in 1.2 mg/kg of Cr Cl3, 2.0mg/kg of Cr-Pic and Cr-Met. The contents of Asp, Glu, Gly and Ala in the muscle were significantly effected by Chromium source, supplemental level and the interaction of them.Based on the Cr concents in the hepatopancreas, the biological utilization rate of Cr-Pic and Cr-Met, with Cr Cl3 as standard were 112.50 %、123.17 %。 With the WGR as evaluation index and the Cr Cl3, Cr-Pic and Cr-Met as chromium sources, broken-line model show that the optimal contents of chromium in juvenile Litopenaeus vannamei diets are 1.33, 1.27 and 1.04 mg/kg, respectively. By comparing, the Cr-Met has the highest relative bioavailability, followed by Cr-Pic, and the lowest is Cr Cl3.2. This experiment was conducted to study the effects of different forms and levels of manganese(Mn) on the growth performance, antioxidant activities, tissue Mn content and cytosolic manganese superoxide dismutase(c Mn SOD) gene expression of Litopenaeus vannamei. Treatments supplement of 0, 10, 20, 30, 40 and 60 mg/kg Mn from manganese sulphate(Mn-S) and manganese Methionine(Mn-Met) respectively. Each diet was fed to triplicate groups of L.vannamei(initial body weight: 1.925±0.002 g) in a recirculated fresh water rearing system for 8 weeks. The results showed that with the increase of Mn concents the weight gain rate(WGR) showed a trend of first increased and then declined.The highest WGR were observed in the 30 mg/kg Mn-S and 20 mg/kg Mn-Met. The lowest protein efficiency ratio(PER), and the highest feed conversion rate(FCR) were observed in prawns fed the control diet(P<0.05) and showed no significant differences among other treatments(P>0.05). Survival rate(SR) were not affected by the dietary treatments(P>0.05). The activities of PO, T-SOD, Mn-SOD and the contents of MDA were significantly affected by manganese sources, supplemental levels and the interaction of manganese sources and supplemental levels(P<0.05). The highest activities of PO,T-SOD, Mn-SOD were founded in the 30 mg/kg Mn-S and 20 mg/kg Mn-Met. On the contrary, the malondialdehyde(MDA) contents were lowest in them. The m RNA expression of c Mn SOD gene in the hepatopancreas of prawns were upregulated with increasing dietary Mn levels, the highest expression were observed in the 60 mg/kg Mn-S and 40 mg/kg Mn-Met. The manganese sources had no significant infiuence on the Mn concentrations in the hepatopancreas and muscles(P>0.05), the supplemental levels had significant infiuence on it(P<0.05), meanwhile the interaction of manganese sources and supplemental levels had no significant infiuence on it(P>0.05). The Mn concentrations in the hepatopancreas and muscles were increased with the increasing of dietary Mn supplementation levels. Based on the Mn concents in the hepatopancreas, the biological utilization rate of Mn-Met, with Cr Cl3 as standard was 115.16 %。 Broken-line regression analysis of Mn-SOD activity, the optimal dietary Mn requirements for juvenile L.vannamei were 33.00 mg/kg Mn-S and 24.77 mg/kg Mn-Met, respectively. The biological utilization rate of Mn-Met was 139.03% compared to Mn-S. Broken-line regression analysis of WGR indicated that the optimal dietary Mn requirements for juvenile L.vannamei were 32.03 mg/kg Mn-S and 21.61 mg/kg Mn-Met, respectively.