Ffects Of Dietary Vitamin E Levels On Growth, Immunity And Resistance To Stress Of Wuchang Bream (Megalobrama Amblycephala)

An90days feeding trial was conducted to estimate the adequate dietary vitaminE (Ve)requirement of Wuchang bream (Megalobrama amblycephala) and its effect on growth,.hematology and muscle physiochemical indexes.420healthy fish were selected andrandomly divided into seven groups that Ve were supplemented at0mg/kg (the controlgroup),12.5,25,50,100,200and400mg/kg (the treated groups)(the analyzed Ve levels were0.5,13.4,27.8,54.7,107.5,197.5and389.6mg/kg diet).1. Effects of dietary vitamin E on growth performance, hematology and musclephysiochemical indexes of Wuchang bream (Megalobrama amblycephala)Weight gain rate (WGR), specific growth rate (SGR) were significantly higher ingroups supplemented with12.5,25,50,100and200mg/kg Ve (P<0.05) and he feedingrate was significantly higher in the groups supplemented with25,50,100and200mg/kgVe than these of the control group.2) Meanwhile, triacyglycerol (TG), aspartateaminotransferase (AST) and alanine aminotransferase (ALT) activities of plasma weresignificantly (P<0.05) lower in groups supplemented with12.5,25,50,100and200mg/kgVe, the total cholesterol and high density lipoprotein cholesterol (HDL-C) of plasma lowerin groups supplemented with12.5,25,50mg/kg Ve and plasma alkaline phosphatase(ALP) was significantly higher in the fish fed100mg·kg-1Ve than these of the controlgroup.3) Muscle crude protein contents significantly (P<0.05) increased in the fish fed12.5,25,50,100and200mg/kg Ve compared with the control group. Muscle cooking meatrate was significantly higher in the fish fed50and100mg·kg-1Ve, while muscle drip lossin the fish fed50and100mg·kg-1Ve diets was significantly (P<0.05) lower than those fed the control diet. Our results suggest that ingestion of a basal diet supplemented with50-200mg/kg Ve can enhance meat quality and the growth of Wuchang bream to someextent.Based on the weight gain with Quadratic curve regression equation model analysesat this study, the optimum vitamin E level in the diet is estimated to be138.5mg·kg-1of dietfor Wuchang bream.2. Effects of Vitamin E on non-specific immunity, hepatic cell ultrastructure and HSP70mRNA expression of M. amblycephala under high temperature stress and recoveryAfter90days feeding, fish（groups supplemented with0,50and400mg/kg Ve）wereexposed by32℃high temperature stress for1day and recovered by25℃temperature for7days in the temperature controlled aquariums.The results showed that before stress,compared with the control, the50mg/kg Ve group significantly decreased the levels ofserum cholesterol (TC) and high density lipoprotein cholesterol (HDL-C)，increased theactivity of intestine glutathione (P<0.05); after stress, compared with the control, the50mg/kg Ve group significantly decreased the levels of serum aspertate aminotransferase(ALT) and cortisol(COR), decreased the levels of serum alanine aminotransferase(AST),TC and COR after7d recovery, while the levels of serum alkaline phosphatase(ALP),intestine glutathione(GSH) and superoxide dismutase(SOD) were significantly improved(P<0.05). The levels of serum ALT, COR and intestine malonaldehyde(MDA) in fish fedthe diet with400mg/kg Ve were significantly reduced after stress and1d recovery, after7drecovery, after stress and7d recovery respectively; while the levels of serum ALP,triiodothyronine (T3) were significantly improved after stress and7d recovery, after stressrespectively(P<0.05). However, hepatic cell ultrastructure and HSP70mRNA expressionwere not significantly different among groups (P>0.05). So it is suggested that ingestion ofa basal diet supplemented with Ve (50-400mg/kg diet) could help regulate the change ofblood lipids,improve antioxidant capacity, also help alleviate high temperature stress onWuchang bream blood biochemical effects, reduce lipid peroxdation,enhance resistanceagainst high temperature stress of Megalobrama amblycephala.3. Effects of emodin on resistance to ammonia nitrogen stress and Aeromonas hydrophilainfection of Wuchang bream (Megalobrama amblycephala) under two temperaturesnitricBesides,After90days feeding, other groups(supplemented with12.5、25、100and200mg/kg Ve)were exposed to high ammonia nitrogen stress (10mg/L) for7days and afterstress infected with Aeromonas hydrophila. the serum immunological and intestinal antioxidant indices were investigated, respectively. The results showed that before stress,compared with the group of12.5mg/kg Ve, the intestinal MDA levels in the group of200mg/kg Ve were significantly reduced(P<0.05), but intestinal SOD levels in the group of200mg/kg Ve were increased significantly (P<0.05), which indicate Ve (as a free radicalscavenger and lipid antioxidant) could improve intestinal antioxidant capacity when add tothe food.After stress and infection, compared with the group of12.5mg/kg Ve, each groupsignificantly decreased the levels of serum ALT and COR after stress and infection for1d,The levels of serum AST and COR were significantly reduced after infection for2d in fishfed the diet with100mg/kg,100and200mg/kg Ve respectively; Whereas the levels ofserum ALP and COR in fish fed the diet with100and200mg/kg Ve were significantlyincreased after stress and infection. This indicated that amount of Ve could help alleviatethe effecto of stress and infection in Wuchang bream to some degree.compared with the group of12.5mg/kg Ve, the levels of serum MDA in fish fed thediet with100and200mg/kg Ve were significantly reduced after infection for2d, and thelevels of intestinal SOD in fish fed the diet with25and100mg/kg Ve were significantlyimproved (P<0.05).The200mg/kg Ve group also significantly improved the levels ofintestinal SOD after infection. Other indices, such as GSH were not significantly differentamong groups (P>0.05).Statistic data also showed that after infection with A. hydrophila,mortality of100and200mg/kg Ve groups were lower than these of the12.5and25mg/kgVe group. Thus, the basal diet supplemented with vitamin E can inhibited the declineddegree of the activity of SOD，clear free-radicals which organism oxidation produceeffectively，improve anti-stress ability of Wuchang bream, enhance disease resistance offish against pathogenic infection.