Effects Of Vitamin E On Growth Performance, Meat Quality And Immune Responses In Channel Catfish, (Ictalurus Punctatus Rafinesque)

It is discovered that vitamin E is a substance in animal body with general physiological functions,such as growth promoting,improving meat quality,anti-oxidization,promoting the reproductive ability and enhancing immune function,etc.At present,the function and the most suitable dosage of vitamin E for the aquatic animals would be the highlights of our researches.Channel catfish,a kind of fresh water fish living in warm water,has become one of main variety in our fresh water aquaculture in China with the characteristics of easy to raise and process, tender meat.In recent years,the researches of channel catfish at home and abroad were mainly focusing on the reproductive biology and disease control,with few reports about the effect of vitamin E on growth performance,immune function and meat quality of channel catfish.The effect of vitamin E in different dosage in feed to Channel Catfish(Ietalurus punetaus Rafinesque) was studied on such fields as the growth performance,the activity of digestive enzymes,morphostructure of alimentary tracts,meat quality,physiological and biochemical indexes of blood,anti-oxidization system in the serum and nonspecific immunity, etc.,and initially discusses the relative mechanism.The effect of Vitamin E in different dosage to the content of IL-2 in the serum of Channel Catfish was studied in molecular level,in order to enrich the experimental data on relative researches in the future and furthering the marketing of harmless channel catfish production.This research included 7 experiments as following:Experiment 1:The experiment was conducted to determine the effects of vitamin E on the growth performance and activities of digestive enzymes of Channel Catfish,Ictalurus punctatus Rafinesque,and probe into mechanism tentatively.900 healthy Channel Catfish(5.00±0.50g of average weight)were randomly divided into four groups,each group included three replicates of 75 Channel Catfish.Groupâ… was supplemented with 0 IU·kg^-1 vitamin E,another three treatments were supplemented consecutively with 50 IU·kg^-1 vitamin E for groupâ…¡,100 IU·kg^-1 vitamin E for groupâ…¢,1000 IU·kg^-1 vitamin E for groupâ…£.The experiment lasted for 105 days.The result showed that vitamin E could improve the survival rate,special weight growth rate(SGR),protein efficiency ratio and feed quantity of Channel Catfish notably(P＜0.01).When vitamin E were 100 IU·kg^-1 diet,the fish had the maximal survival rate,special weight growth rate,protein efficiency ratio and feed quantity(97.78±0.96 %,2.99±0.50%,163.71±5.62%and 7478.00±62.01 g/tail),higher than the vitamin E adding amount for groupâ… extremely notably (P＜0.01).What's more,vitamin E had significant effect on protease, lipase in the gastrointestinal tract and hepato-pancreas of Channel Catfish(P＜0.01 or P＜0.05).Vitamin B were 100 IU·kg^-1 diet,Channel Catfish had the maximal the activities of protease,lipase(29.33±1.66 U·min^-1·mg^-1,196.52±17.28 U·min^-1·mg^-1),higher than the vitamin E adding amount for groupâ… extremely notably(P＜0.01)and higher than groupâ…£notably(P＜0.05).Therefore,these results indicate that vitamin E could improve the growth,activities of digestive enzymes of Channel Catfish in a certain level.Experiment 2:The effect of vitamin E in different dosage on the height of intestinal fold,the thickness of intestinal mucosa,the number of mucous cells and the expression of SS of Channel Catfish was studied by the methods of histology,immunohistochemistry and graphical analysis. The test results demonstrated that vitamin E could significantly increase the height of intestinal fold,the thickness of intestinal mucosa,the number of mucous cells,the expression of SS and the number of positive cells(P＜0.01or P＜0.05) in a certain level.When the amount of vitamin E reached to I00 IU·kg^-1,these four indexes above came to the highest, which were extremely higher than those in groupâ… (P＜0.01or P＜0.05), while not significant with groupâ…¡andâ…£(P＞0.05).When the amount of vitamin E reached to 1000 IU·kg^-1,these indexes in groupâ…£have tended to decline while not significant with groupâ…¡andâ…¢(P＞0.05).Experiment 3:The effect of vitamin E in different dosage on the quality of meat of Channel Catfish was studied,and the relative mechanism was initially discussed.The test results of meat quality indicated that vitamin E could affected the proper index which affects the quality of meat,physical characteristics and nutrient content of Channel Catfish, such as improving the scent,color,texture and flavor of meat,raising the content of crude protein,inosinic acid and delicious substance of meat,and decreasing the content of malondialdehyde.The results also showed that vitamin E could increase the content of collagen in muscular tissue of Channel Catfish.The influence law of vitamin E to the content of collagen was the same as that to the break-resisting force of myofibril, while contrast to the rate of water loss.The break-resisting force of myofibril was positively associated with the content of collagen,while the rate of water loss have a negative correlation with the content of collagen,with the regression lines as y=1.1506+0.5188x(R²=0.9851) and y=27.375-0.4385x(R²=0.9525) respectively.Experiment 4:The effect of vitamin E in different dosage on physiological and biochemical indexes of blood of Channel Catfish was studied.The test results showed that vitamin E could increase or significantly increase the indexes(P＜0.01or P＜0.05) during a given level.When the amount of vitamin E reached to 100 IU·kg^-1,the indexes of RBC,Hb,ALB,GLO,TG,TC,AST,ALT,BUN,AKP,MDA,etc.made sure the fish were at the top of their form,which were significant or extremely significant with those in groupâ… (P＜0.01or P＜0.05),while not significant with groupâ…¡andâ…£(P＞0.05).Experiment 5:The effect of vitamin E in different dosage on the activity of SOD,CAT,GSH-Px and GST in anti-oxidization system in the serum of Channel Catfish was studied through the single factor experiment. The test results demonstrated that vitamin E could significantly affect the activity of SOD,CAT and GST(P＜0.05) in a certain level,while not significant with GSH-Px(P＞0.05).Experiment 6:The effects of vitamin E in different dosage on nonspecific immune function of Channel Catfish were compared,by measuring the weight of immune organs,phagocytic activity of white cells, bactericidal index of phagocytic cells,the content of lysozyme in serum and complement C₃ and survival rate after the challenge of toxic substances. The test results of nonspecific immunity indicated that vitamin E could significantly affect the body indexes of head-kidney and spleen, phagocytic activity of white cells,bactericidal index of phagocytic cells,the content of lysozyme in serum and complement C₃ and survival rate after the challenge of toxic substances(P＜0.01) in a certain level, while not significant with the body index of kidney(P＞0.05).Experiment 7:A part of IL-2 gene of Channel catfish were cloned by RT-PCR and the recombinant plasmid was constructed as the positive pattern plate in order to establish the FQ-PCR method of IL-2 gene of channel catfish.Through this established method,the contents of IL-2 of channel catfish in different test groups were measured.The results of IL-2 tests showed that vitamin E could significantly provoke the secretion of IL-2(P＜0.05)so as to improve the immunity of Channel catfish.Above all,in a certain level,vitamin E could improve the growing development of alimentary organs,boost the activity of digestive enzyme, and raise the absorbency of intestinal tract so that to increase the production performance of channel catfish and efficiency of feed utilization.Vitamin E could not only improve the meat quality of Channel Catfish,but also enhance the nonspecific immunity and the oxidation resistance of anti-oxidization system in serum.