Effects Of Dietary Vitamin D₃Levels On Growth, Non-Specific Immunity And Anti-Pathogenic Of Wuchang Bream（Megalobrama Amblycephala, YIH）

A90-day feeding experiment was conducted to estimate the effect of dietary vitamin D3levels on growth, non-specific immunity and ati-pathongenic of juvenile Wuchang bream (Megalobrama amblycephala). Casein was used as Protein source, dextrin as sugar source and soybean oil as lipid source. Six isonitrogenous and isoenergentic purified diets containing0,500,1000,2000,4000and8000IU/kg vitamin D3(supplied as cholecalciferol, D3), Each diet was fed to four replicate groups of fish (initial weight20.60±0.15g/fish) in the breeding system of automatic temperature control with circle water.1. Effects of vitamin D3on growth, physiological and biochemical parameters of Wuchang bream. Fish fed the basal diet (Diet OIU/kg vitamin D3) showed many vitamin D3deficient syndrome at the end of experiment, such as:poor growth, slow swimming, lighter in body color, transparent skull etc. After45days of feeding, the results showed that compared with the control (non vitamin D3), the group of2000IU/kg vitamin D3diet could markedly elevate the growth index of Wuchang bream. After90days of feeding, the results were summarized as follows:The weight gain, specific growth rate, feed efficiency ratio were significantly reduced in OIU/kg treatment, but they were not apparently different in500IU/kg-8000IU/kg treatments. The body and muscle composition analysis showed that body and muscl ash content, calcium content were significantily elevated with vitamin D supplements. The analysis of serum parameters showed that:compared with the control,500IU/kg and1000IU/kg vitamin D3groups significantly improved the levels of serum Calcium ion and inorganic phosphorus, alkaline phosphatase and reduced the levels of serum triglycerides of Wuchang bream. So ingestion of500IU/kg-1000IU/kg doses of vitamin D3could improve serum Calcium ion and inorganic phosphorus of Wuchang bream. It is concluded that the optimum requirement of juvenile Wuchang bream for vitamin D3is about1000IU-2000IU/kg diet in aquaculture product.2. Effects of vitamin D3on non-specific immunity and HSP70mRNA expression of Wuchang bream. A trial was conducted to study the influenees of different levels of vitamin D3on The biochemical parameters of blood and liver, and expression levels of liver HSP70mRNA of juvenile Wuchang bream. The results showed that, compared with the control, serum alkaline phosphatase, total protein, albumin, C4levels, liver superoxide dismutase, peroxides activities and expression levels of HSP70mRNA increased in1000IU/kg and2000IU/kg groups in varying degrees and serum aspartate aminotransferase and cortisol, levels decreased to some extent. These data suggest that Wuchang bream feed1000IU/kg-200IU/kg vitamin D3diet can promote non-specific immunity and HSP70mRNA expression of Wuchang bream.3. Effects of vitamin D3on biochemical parameters of Wuchang bream infected with Aeromonas hydrophila. At the end of the rearing experiment, take10fish per tank were intraperitoneally infected with A. hydrophila (BSK-10), and the biochemical parameters of serum and liver, the mRNA expression levels of liver HSP70genes before and after infection were determined. Another ten fish taken from each tank were challenged with A. hydrophila as the same method as above, the cumulative mortality of each group was counted at different time point of post-infection. The results showed that after infection of fish, compared with the control, serum total protein, albumin, C3, C4and alkaline phosphatase levels, liver superoxide dismutase, peroxides activities, total antioxidant capacity activities, and the expression level of HSP70mRNA increased in1000IU/kg,2000IU/kg and4000IU/kg groups in varying degrees, while serum cortisol, aspartate aminotransferase levels decreased to some extent. Statistics also showed that after infected with A. hydrophila, the cumulative mortalities of2000IU/kg groups were significantly lower than that of control group.4. Effects of high doses of vitamin D3on growth, physiological and biochemical parameters and the mRNA expression levels of liver HSP70genes of Wuchang bream. A90-day feeding experiment was conducted to estimate the effect of dietary vitamin D3levels on growth and serum biochemical parameters for juvenile Wuchang bream. Two isonitrogenous and isoenergentic purified diets containing2000,200000IU/kg vitamin D3(supplied as cholecalciferol, D3) per kg diet. Each diet was fed to four replicate groups of fish (initial weight21.40±0.35g/fish) in the breeding system of automatic temperature control with circle water. The results showed that compared with the control(2000IU/kg), the weight gain, specific growth rate, the levels of serum glucose, aspartate aminotrans-ferase, cholesterol, alkaline phosphatase, and other biochemical indexin in200000IU/kg group decreased to some extent, but most of them were not significantly different from the control (P>0.05). While the liver peroxides activities, total antioxidant capacity activity, serum cortisol COR, insulin INS and the expression levels of liver HSP70mRNA decreased significantly (P<0.05). Using tissue sliein to study the effeets of dietary vitminD3levels on the intestinal structure and liver structure of Wuchang bream. Adding too much vitaminD3(200000IU/kg) in diet led to damaging the intestinal structure and liver structure of Wuchang bream.