Studies On Nutritional Physiology Of Zinc And The Interaction Between Zinc And Copper In Abalone, Haliotis Discus Hannai Ino

The studies were conducted to assess the effects of dietary zinc,interaction between dietary zinc and copper on the growth,physiology and antioxidant capacity of abalone(Haliotis discus hannai Ino),and also investigate effects of dietary zinc and copper on metallothionein gene expression.Experiment 1 was conducted to determine the response of juvenile abalone,H. discus hannai,to dietary zinc deficiency and excess.Zinc sulfate(ZnSO₄·7H₂O) were used as the sources of dietary zinc.Three casein-gelatin-based diets containing three graded levels of zinc(deficient,no-supplementary;normal,35mg/kg;excessive, 3500mg/kg) were fed to the animals.After 28 weeks of feeding,the animal's survival, growth,soft-body concentration of moisture,lipid,protein and mineral elements,shell concentration of ash and mineral elements,and hepatopancreas activities of alkaline phosphatase(AKP),superoxide dismutase(SOD),catalase(CAT),glutathione peroxidase(GPX) and total antioxidant capacity(T-AOC) were measured.The results showed that dietary zinc content significantly affected the weight gain rate(WGR) and soft-body concentration of protein(P＜0.05),the survival,daily increase of shell length (DISL),soft-body moisture,soft-body lipid and shell ash have no significant difference among treatments(P＞0.05);the concentrations of hepatopancreas zinc,muscle zinc and iron,hepatopancreas activities of AKP,SOD,GPX and T-AOC significantly increased with dietary zinc(P＜0.05).Meanwhile,the mineral elemental concentration in shell and hepatopancreas CAT activity showed no significant difference(P＞0.05).In experiment 2,a 3×3 feeding experiment was conducted to determine the response of juvenile abalone,H.discus hannai,to dietary zinc,copper and the interaction between the two.Zinc sulfate(ZnSO₄·7H₂O) and copper sulfate (CuSO₄·5H₂O) were used as the sources of zinc and copper.Nine casein-gelatin-based diets containing three graded levels of zinc(no-supplementary,normal 35mg/kg,excess 700mg/kg) for each of three levels of copper(no-supplementary,normal 4mg/kg,excess 80mg/kg) were fed to the animals previously fed a basal diet(normal zinc and copper concentration)for 14 days.After 28 weeks of feeding,the animal's survival,growth, soft-body concentration of moisture,lipid,protein and mineral elements,shell concentration of ash and mineral elements,and hepatopancreas activities of alkaline phosphatase(AKP),superoxide dismutase(SOD),catalase(CAT),glutathione peroxidase(GPX) and total antioxidant capacity(T-AOC) were measured.The results showed that the weight gain rate(WGR),daily increment in shell length(DISL), soft-body concentration of protein,the hepatopancreas activities of AKP,SOD,GPX, T-AOC,and zinc,iron concentration in hepatopancreas,zinc concentration in muscle were significantly affected by dietary zinc levels positively(P<0.05),and only on condition of sufficient of excess dietary copper,the normal level of dietary zinc can increased the iron concentration in hepatopancreas significantly;the weight gain rate (WGR),daily increment in shell length(DISL),soft-body concentration of protein,the hepatopancreas activities of AKP and T-AOC,zinc and copper concentration in hepatopancreas,copper concentration in muscle were significantly affected by dietary copper levels positively(P<0.05);only three parameters:soft-body concentration of protein,iron concentration and AKP activity in hepatopancreas,were significantly affected by the interaction of the two trace elements(P<0.05).Metallothionein(MT) is a superfamily of cysteine-rich proteins contributing to metal metabolism,detoxification of heavy metals,and immune response such as protecting against ionizing radiation and antioxidant defense.In experiment 3,after feeding the abalone with diet varying in 4 levels of zinc(deficient no-supplementary, normal 35mg/kg,excess 700mg/kg and extreme excess 3500mg/kg) and 3 levels of copper(no-supplementary,normal 4mg/kg,excess 80mg/kg),tissue specificity expression analysis has been taken to detection of MT transcripts by SYBR-Green I Real-time PCR.β-actin was taken as the internal control.The results of Real-time PCR can be analyzed through the Detla Detla C_T comparative method together with Melt Curve analysis.By taken internal control the tissue specificity expression analysis showed that the hepatopancreas MT transcripts are significantly abundant when the dietary zinc or copper are sufficient or excess,the mantle MT expression is significantly affected by dietary zinc concentration,too,but the dietary copper level does not have significant influence on it.As a conclusion,the expression of matallothionein gene in hepatopancreas might be a useful parameter in mineral element nutrition research of abalone.