Effect Of Dietary Oxidized Oil On Growth,Antioxidation And Intestinal Health Of Channel Catfish(Ictalurus Punctatus) And Tilapia(Oreochromis Niloticus) And The Intervention Of Tea Polyphenol On Oxidized Oil

Exp 1 Effect of dietary oxidized oils on the growth,antioxidant indexes and body color of channel catfish(Ictalurus punctatus)The present study was conducted to investigate the effects of dietary oxidized fish oil(OFO)and oxidized soybean oil(OSO)on the growth,body color and antioxidant ability of channel catfish,Ictalurus punctatus.The eight diets containing 0,20,40,60 g/kg OFO or OSO,were prepared and fed to triplicate groups of channel catfish(150.5±4.2 g)for 8 weeks.The results showed that weight gain(WG)reduced(P<0.05),and feed conversion ratio(FCR)increased with the increasing OFO or OSO in diets(P<0.05).Groups of OFO-40 and OSO-40 showed a lower WGR(-13.5%,-4.6%)and a higher FCR(0.2,0.08)than the control of OFO-0 and OSO-0(P<0.05),respectively.With the increase of dietary oxidized oil,the b* value(yellowness)of dorsal and caudal skin,the contents of malondialdehyd in serum and liver,the content of total bilirubin,direct bilirubin and the activity of alanine aminotransferase,aspartate aminotransferase in serum increased(P<0.05),and the glutathione level in serum and liver decreased(P<0.05).The activities of catalase and superoxide dismutase in serum showed the maximum values when the oxidized oils inclusion reached 20 g/kg.The above results showed that the growth performance was decreased,skin yellowness was increased,and the antioxidant capacity in liver was damaged when dietary oxidized oil reached 40 g/kg.Oxidized fish oil caused more negative effects on the fish than oxidized soybean oil at the inclusion level of 40 g/kg.Exp2 Dietary tea polyphenol alleviated the negative effects of oxidized oil on the growth,digestion and intestine healthy of tilapia,Oreochromis niloticus×O.aureusTo investigate the effects of oxidized soybean oil(OSO)on the growth,digestive function and intestinal health of hybrid tilapia(Oreochromis niloticus×O.aureus)and the intervention of tea polyphenol(TP)on the damage of oxidized soybean oil.A two-factor test(3×2)was designed by supplementing 0,400 mg/kg tea polyphenols to three feeds with 0,15 and 30 g/kg OSO.Six iso-nitrogenous and iso-lipidic diets were prepared and fed triplicate groups of hybrid tilapia with an initial weight of(6.09±0.07 g).After 9 weeks feeding,the weight gain(WG)of OS-30 decreased by 9.8%,and feed conversion ratio(FCR)increased by 0.10(P<0.05),when compared with the control group(OS-0).The supplementation of 400 mg/kg TP in OS-0 and OS-15 diets did not affected the WG(P>0.05),but the supplementation in OS-30 diet increased the WG(P<0.05),and reached the similar level as control group.Compared with the control group,apparent digestibility of dry matter and protein,intestinal protease activity,total bacterial amount,villus length and goblet cell amounts were significantly reduced in groups of OS-15 and OS-30(P<0.05).Besides,the OS-30 group showed lower activities of amylase and catalase,lower lactic acid bacteria amount and glutathione level(P<0.05),and higher Escherichia coli amount and malondialdehyde level(P<0.05)than control group.The supplementation of 400 mg/kg TP in OS-15 and OS-30 significantly increased the apparent digestibility of dry matter and protein,intestinal protease activity and villus length(P<0.05),and decreased the amount of Escherichia coli and the level of malondialdehyde(P<0.05).The supplementation of TP in OS-30 significantly increased the activity of amylase and catalase,the level of glutathione,the amount of total bacteria and lactic acid bacteria(P<0.05),but the amount of total bacteria was still lower than control group(P<0.05).In conclusion,oxidized soybean oil reduced the growth performance,intestinal bacterial level,nutrientdigestibility,and damaged the intestinal mucosal structure of hybrid tilapia.The supplementation of 400 mg/kg tea polyphenols could eliminate the negative effects of oxidized soybean oil on growth and intestinal health.Exp 3 Effect of dietary tea polyphenol on growth,digestion,immune and disease resistance capability of hybrid tilapia(Oreochromis niloticus × O.aureus)The objective of the present study was to investigate the effects of dietary tea polyphenol(TP)on the growth,digestion,immune and resistance ability against Aeromonas hydrophila of hybrid tilapia(Oreochromis niloticus × O.aureus).Six diets were designed to contain 0(control group),100,200,400,600,800 mg/kg TP,and fed to triplicate groups of 25 fish with an initial body weight of(6.09±0.07 g).After 9 weeks feeding,dietary TP showed no significant effects on the growth(P>0.05),but weight gain firstly increased and then decreased with the increase of dietary TP.Whole body moisture,crude protein and ash levels,and crude protein digestibility showed no significant difference among groups(P>0.05),but the high inclusion of TP(600-800 mg/kg)significantly decreased the activities of amylase and protease of foregut as well as dry matter digestibility(P<0.05).Serum activities of superoxide dismutase(SOD)and lysozyme(LZM)were promoted by dietary TP at 200-800 mg/kg inclusion(P<0.05),and serum malonaldehyde(MDA)level increased firstly and then decreased with the increase of dietary TP.The maximum SOD and minimum MDA were observed in 200 mg/kg TP group and the maximum LZM was observed in 400 mg/kg TP group(P<0.05).After the infection of Aeromonas hydrophila,the mortality was significantly decreased by the supplementation of 200-800 mg/kg TP(P<0.05),and 400 mg/kg TP group had the lowest mortality among groups.In a conclusion,dietary TP could promote the immune function and resistance ability against Aeromonas hydrophila,but have no significant effect on growth of tilapia,the optimal dietary TP supplementation issuggested to be 200-400 mg/kg.