Effects Of Dietary Linolenic Acid Levels On Growth,Antioxidant Capacity And Lipid Metabolism Of Rhynchocypris Lagowskii Dybowski

The present study was conducted to explore of dietary linolenic acid levels on growth,antioxidant capacity and lipid metabolism of Rhynchocypris lagowskii Dybowski [initial weight(6.63±0.01)g/tail].Corn oil,palm oil and linseed oil as the main fat sources,fish meal and casein as the main protein sources,flour as the main sugar source,cellulose as the filler,six diets containning different linolenic acid levels(0.0%,0.27%,0.53%,0.80%,1.07%,1.33%)were fed for 8 weeks.The results showed as followed: 1.Effects of dietary linolenic acid level on the growth,dietary utilization and muscular nutritionWith the increase of dietary linolenic acid content,the final body weight(FBW),weight gain(WG),specific growth rate(SGR),feed efficiency rate(FER)and protein efficiency rate(PER)were firstly increased and then decreased.The FBW,WG and SGR showed a significantly higher in the 0.53%,0.80% and 1.07% groups(P<0.05).FER were the highest in the 0.53% group(P<0.05).By regression analysis of SGR,the most suitable linolenic level was 0.79%.Under the current conditions,the crude protein content in muscle firstly increased and then decreased with the increase of dietary linolenic acid,and showed a significant higher in the 0.53%,0.80% and 1.07% groups(P<0.05).Crude fat content increased gradually with the increase of linolenic acid content,and was significantly higher in the groups of 0.27%,0.53%,0.80%,1.07% and 1.33%(P<0.05).2.Effect of dietary linolenic acid level on the digestive enzyme activityWith the increase of dietary linolenic acid level,the intestinal and hepatopancreatic protease activity firstly increased and then decreased,the intestinal and hepatopancreatic protease activity was significantly higher in the linolenic acid level of 0.53% and 0.80%(P<0.05).The intestinal lipase activity intestine firstly increased and then decreased with the increase of linolenic acid content in dietary.At the linolenic levels of 0.80%,the activity of lipase in the foregut,midgut and hindgut were significantly higher(P<0.05).With the increase of dietary linolenic acid level,the activity of amylase in the foregut and hindgut firstly increased and then decreased.When the level of linolenic acid was 0.53%,the activity of amylase in the midgut was significantly higher(P<0.05).3.Effect of dietary linolenic acid level on non-specific immune indexThe lysozyme(LZM),alkaline phosphatase(AKP)and acid phosphatase(ACP)activities in the hepatopancreatic firstly increased and then decreased with the increase of dietary linolenic acid level.The activities of LZM,AKP and ACP in the hepatopancreatic of 0.53% and 0.80% groups were significantly increased(P<0.05);The activities of aspartate aminotransferase(AST)and alanine aminotransferase(ALT)in the hepatopancreatic firstly increased and then decreased,and the AST of 0.53% group showed a highest value(P<0.05).The ALT activities in the 0.53% and 0.80% groups were significantly higher(P<0.05).4.Effect of dietary linolenic acid level on antioxidant capacityThe activities of catalase(CAT),superoxide dismutase(SOD),glutathione s-transferases(GST)and glutathione reductase(GRAC)firstly increased and then decreased with the increase of dietary linolenic acid level,and the activity of 0.80% group was significantly higher(P<0.05).glutathione peroxidase(GSH-PX)activity reached the highest in the 0.53% group(P<0.05).The activity of malondialdehyde(MDA)in hepatopancreas firstly decreased and then increased,and the values of 0.53%,0.80% and 1.07% were significantly lower(P<0.05).5.Effect of dietary linolenic acid level on metabolic enzyme activityThe activities of lipoprotein lipase(LPL),high-density lipoprotein(HDL-C)and low-density lipoprotein(LDL-C)in hepatopancreas firstly increased and then decreased with the increase of linolenic acid content in the diet,the LPL and LDL-C activities of the 0.80% group was significantly higher(P<0.05).In the 1.07% group,the HDL-C activity was significantly higher(P<0.05).Malate dehydrogenase(MDH)and triglyceride(TG)increased with the increasing the dietary linolenic acid levels,MDH in hepatopancreas of 0.27%,0.53%,0.80%,1.07%,and 1.33% groups showed a higher value(P<0.05),and the TG content in the 0.80%,1.07% and 1.33% groups were significantly higher(P<0.05).6.Effect of dietary linolenic acid level on fatty acid compositionThe content of saturated fatty acid C14:0 and the total amount of SFA in muscle decreased with the increase of linolenic acid level.The contents of linolenic acid(C18:3n-3),EPA(C20:5n-3)and DHA(C22:6n-3)increased with the increase of linolenic acid content in diet.The content of linolenic acid,EPA and DHA in 1.07% and 1.33% groups were significantly higher(P<0.05).The total amount of PUFA showed a increasing trend with the increase of linolenic acid level.The content of C14:0 in the hepatopancreas decreased with the increase of linolenic acid level in the die.The content of C18:3n-3,EPA and DHA levels were significantly higher in the 0.53%,0.80%,1.07% and 1.33% groups(P<0.05).The PUFA increased with the increase of linolenic acid.Under the current conditions,the suitable dietary linolenic acid level can improve the growth performance,digestive enzyme activity,antioxidant capacity and lipid metabolism enzyme activity of juvenile Rhynchocypris lagowskii Dybowski.The suitable dietary linolenic acid level of juvenile Rhynchocypris lagowskii Dybowski was 0.53%-0.80%.