Studies On Iron Requirements Of Juvenile Rainbow Trout (Oncorhynchus Mykiss) And Starry Flounder(Platichthys Stellatus)

This experiment was conducted to investigate the effects of differentadditional dietary ferrous fumarate on growth performance, blood biochemicalparameters and trace elements accumulation of whole body and tissues in rainbow trout(Oncorhynchus mykiss). Total of360juvenile rainbow trout (initial weight89.2±0.2g)were selected and randomly allotted to6groups with3replications containing20fish,uptake purified diets supplemented with ferrous fumurate (0mg,20mg,40mg,80mg,160mg,480mg iron per kg diet）in basal diets. Every experimental group was namedD0, D20, D40, D80, D160and D480, D0as the control group, containing measured iron62.6mg,79.5mg,99.6mg,139.3mg,215.2mg,538.4mg iron per kg feed respectively.The fish were fed twice one day (8:00and16:30), feed intake1.5%-2%of body weightdaily during60days experiment. Results indicated that (1) weight gain rate (WGR),specific growth rate (SGR), feed conversion rate (FCR), hepatosomatic index (HSI),viscerosomatic index (VSI) and survival rate (SR) of juvenile rainbow trout were notaffected by different dietary iron levels(P＞0.05).(2) Haemoglobin (Hb) increased firstand then level off from group D40. Haemoglobin (Hb) in group D40、D80、D160andD480were significantly higher than group D0(P＜0.05). The amount of red blood cells(RBC) also increased first and then level off, group D80、D160and D480significantlyhigher than group D0and D20(P＜0.05). No significance was found in haematocrit(Hct, P＞0.05).(3) Iron contents in whole body, vertebrae and muscle increasedsignificantly with increasing dietary iron (P＜0.05). Iron concentrations in liverincreased significantly(P＜0.05) and then leveled off from group D40to group D480,D40、D80、D160and D480significantly higher than group D0and D20(P＜0.05). Nosignificant differences were found among dietary treatments in zinc contents of wholebody (P＞0.05). Zinc contents in control group of vertebrae and muscle weresignificantly higher than those of other groups(P＜0.05) and there were no significantdifferences in other groups(P＞0.05). Zinc concentrations of liver in group D0andgroup D20were significantly higher than those of other groups(P＜0.05). Coppercontents in whole body increased significantly with increasing dietary iron (P＜0.05), control group significantly lower than other groups(P＜0.05). Copper concentration ofcontrol group was significantly lower than those of other groups in muscle(P＜0.05)and no significant difference was observed in vertebrae (P＞0.05).(4) Serum lysozyme(LZM)of group D0was significantly lower than group D20、D40、D80and D160(P＜0.05), but there were no significantly differences between group D0and group D480(P＞0.05). Catalase (CAT) of serum was enhanced significantly(P＜0.05) from D0to D40and then decreased obviously(P＜0.05) and group D40was significantly higher thanother groups(P＜0.05). Based on haemoglobin and iron content in liver response, usingthe broken-line model, the requirements of iron provided with ferrous fumarate forjuvenile rainbow trout (Oncorhynchus mykiss) were estimated to be99.8mg/kg and100.4mg/kg respectively in the experiment.The basal diet provided with casein-gelatin as protein sources and fish oilas lipid source was supplemented with different levels of ferrous fumarate（0mg,20mg,40mg,80mg,160mg,480mg iron per kg diet）to produce six purified diets namedgroup D0, group D20, group D40, group D80, group D160and group D480, group D0as the control group, containing measured iron23.90、41.37、60.83、105.20、182.50and505.40mg iron per kg diet. Juvenile starry flounder (Platichthys stellatus), initialweight (43.5±0.2) g, were fed to satiation twice (8:00and17:00) per day for8weeksto investigate the effects of different additional dietary ferrous fumarate on growthperformance, blood biochemical parameters, metabolism of serum iron and traceelements accumulation in whole body and tissues. Results indicated that (1) weight gainrate (WGR) and specific growth rate (SGR) increased significantly with increasingdietary iron content, group D40、D80、D160and D480significantly higher than groupD0(P＜0.05). Feed conversion rate (FCR) decreased significantly, group D80、groupD160and group D480significantly lower than group D0(P＜0.05). Viscerosomaticindex (VSI) and spleensomatic index (SSI) improved significantly(P＜0.05),hepatosomatic index (HSI) in group D480was significantly higher than group D80(P＜0.05). Daily feed intake (DFI), condition factor (CF) and survival rate (SR) were notaffected by dietary iron levels(P＞0.05).(2) With increasing dietary iron levels,haemoglobin (Hb) was enhanced significantly up to group D160and then plateaued,group D160and group D480significantly higher than group D0(P＜0.05). Haematocrit(Hct) improved significantly with increasing dietary iron levels, group D480significantly higher than group D0, group D20and group D40(P＜0.05). No significantdifference was found in the amount of red blood cells (RBC)(P＞0.05).(3) Serum iron contents increased first and then level off from group D80. Serum iron contents ofgroup D80, group D160and group D480were significantly higher than other groups (P＜0.05). Unsaturated iron binding capacity (UIBC) of blood serum decreasedsignificantly(P＜0.05) and UIBC of group D80, group D160and group D480weresignificantly lower than group D0(P＜0.05). Serum iron saturation index improvedsignificantly(P＜0.05), groups provided with iron supplementation higher than groupswithout iron supplementation(P＜0.05). Total iron binding capacity(TIBC) was notaffected by different dietary iron concentrations(P＞0.05). Ceruloplasmin improvedsignificantly up to group D80and then plateaued, group D80、group D160and groupD480significantly higher than group D0(P＜0.05).(4) There were no significantlydifferences in whole body iron content among all groups(P＞0.05). Hepatic ironcontents increased with increasing dietary iron levels and hepatic iron contents in groupD80, group D160and group D480were significantly higher than group D0(P＜0.05).Zinc and copper levels of whole body and liver were not affected by dietary ironcontents(P＞0.05).(5) Serum lysozyme (LZM) of group D480was the highest andthere were no significant differences among other groups(P＞0.05). Total antioxidantcapacity(T-AOC) increased significantly with increasing dietary iron levels(P＜0.05).Catalase (CAT) of serum was enhanced significantly(P＜0.05) from D0to D80and thenleveled off, group D80、group D160and group D480significantly higher than groupD0(P＜0.05). Based on specific growth rate, haemoglobin and serum iron contentresponse, using the broken-line model, the requirements of iron provided with ferrousfumarate for juvenile starry flounder (Platichthys stellatus) were estimated to be121.1mg/kg,115.7mg/kg and106.6mg/kg respectively in the experiment.