Effects Of Dietary Vitamin E And Water Temperature On Growth Performance,Immunity, Antioxidant Capacity And Resistance To Acute Hypoxia Stress In Spotted Seabass (Lateolabrax Maculatus)

An 8-week feeding trial was conducted to investigate the effects of water temperature and dietary vitamin E levels on growth performance,non-specific immunity,antioxidant capacity and resistance to hypoxia stress of spotted seabass(Lateolabrax maculatus)under different water temperatures(27℃,33℃).Six diets were formulated containing 11.4,32.6,52.3,71.4.154.9,316.9 mg vitamin E/kg,DL-α-tocopheryl acetate was used as the vitamin E source,the main research results are as follows:1.Studies on effects of dietary vitamin E and water temperature on growth performance,body composition and concentration of vitamin E spotted seabass under different temperaturesThe weight gain rate,special growth rate and feed efficiency showed an increased firstly then appeared to plateau trend by increasing dietary vitamin E levels at same water temperature and the group offered 53.2 mg vitamin E/kg diet exhibited the highest,the viscerosomatic index showed an increasing firstly then decreasing trend when they were at same vitamin E diets.The weight gain rate,special growth rate and feed efficiency decreased significantly at 33℃,while hepatosomatic index and condition factior were on the contrary trend(p<0.05).A broken-linear regression analysis based on weight gain rate showed that the vitamin E requirements of spotted seabass reared at 27℃ and 33℃ are 55.2 mg/kg and 37.1 mg/kg,respectively.Crude protein of whole body increased by increasing dietary vitamin E levels(p<0.05),while moisture,crude lipid and crude ash of whole body were not significantly affected by dietary vitamin E levels at same water temperature.The crude ash of whole body at 33℃ were decreased significantly(p<0.05)while moisture,crude protein and crude lipid were not significantly affected by water temperature when they were at same vitamin E diets.The vitamin E concentration in liver and mussle increased firstly with increasing dietary vitamin E from 11.4 mg/kg to 71.4 mg/kg then appeared to plateau,the vitamin E concentration in liver and mussle at group fed the vitamin E diet were significantly higher than those at group fed the basal diet(p<0.05),they decreased significantly as the water temperature rised(p<0.05).2.Studies on effects of dietary vitamin E and water temperature on non-specific immunity,antioxidant capacity of spotted seabass under different temperaturesThe complement 3,complement 4 and the activities of Lysozyme at group fed the vitamin E diet were enhanced significantly by increasing dietary vitamin E levels at same water temperature(p<0.05);The complement 3 and complement 4 decreased while the activities of Lysozyme increased significantly by increasing water wemperature when fed with same vitamin E diets(p<0.05).The activities of superoxide dismutase in liver increased and the concentration of Malondialdehyde decreased significantly(p<0.05),while the Catalase and total antioxidant capacity were not significantly affected.The activities of superoxide dismutase and total antioxidant capacity in gill were enhanced significantly while the concentration of malondialdehyde decreased by increasing dietary vitamin E levels(p<0.05).The activities of Catalase and superoxide dismutase in liver decreased and the concentration of malondialdehyde increased significantly(p<0.05),while the total antioxidant capacity were not significantly affected by increasing water temperature when fed with same vitamin E diets.The activities of superoxide dismutase and the total antioxidant capacity in gill decreased and the concentration of malondialdehyde increased significantly(p<0.05)by increasing water temperature.A broken-linear regression analysis based on the concentration of malondialdehyde in liver showed that the vitamin E requirements of spotted seabass reared at 27℃ and 33℃ are 55.9 mg/kg and 56.7 mg/kg,respectively.3.Studies on effects of dietary vitamin E on resistance to hypoxia stress of spotted seabassAfter 8-weeks feeding trail at 27℃,12 fish in each tank were captured and exposed to acute hypoxia stress.The air were expelled by filling in nitrogen,oxygen content in water were reduced from 8.0 mg/kg to 1.0 mg/kg within 2 h,sample were collected in 0 h,1 h,3 h and 6 h.The results showed that the survive rate was not affected by dietary vitamin E and exposure time,expression of HIF-1 and GLUT were not affected by dietary vitamin E.The content of Cortisol in liver and serum Lactate dehydrogenase increased significantly(p<0.05)while serum Glucose performed an increased firstly then decreased trend.As exposure time went by,the content of Cortisol in liver and serum Lactate dehydrogenase were enhanced significantly,serum Glucose and expression of HIF-1 and GLUT performed an increased firstly then decreased trend(p<0.05).