Effects Of Dietary Bile Acid On Growth Performance And Lipid Utilization Capacity Of Turbot (Scophthalmus Maximus)

In recent years,bile acid has been used more and more widely as feed additive in aquaculture.The effects of dietary bile acid at different lipid levels and lipid sources on growth performance,digestive enzyme activity,antioxidant capacity and lipid metabolism were investigated in turbot,Scophthalmus maximus（23.12±0.10 g）.Experiment 1 Four formulated diets with 10%and 14%lipid levels add 0%or 0.09%bile acid respectively to evaluate the effects of growth performance,digestive enzyme activity,antioxidant capacity,lipid utilization.The body weight gain（BWG）was significantly higher by adding 0.09%bile acid,however,feed conversion rate（FCR）and viscerosomatic index（VSI）were significantly decreased（P<0.05）.Lipoprotein lipase,hepatic lipase,total lipase,lipase and amylase were significantly increased（P<0.05）by adding 0.09%bile acid.0.09%bile acid diet can significantly improved the content of EPA（P<0.05）while declined the content of DHA and n-3/n-6 at 10%lipid level,and at 14%lipid level diet produced the opposite effects.SOD,CAT,GSH-Px and T-AOC activities had the trend of increasing supplemented bile acid groups while MDA content decreased.However,the differences were not significant（P>0.05）.Experiment 2 Three formulated diets with 10%(B₁₀),14%(B₁₄)and 18%(B₁₈)lipid levels and by adding 0.09%bile acid respectively to evaluate the effects of growth performance,digestive enzyme activity,antioxidant capacity,lipid utilization.With the increasing lipid level WGR,special growth rate（SGR）and protein efficiency ratio（PER）were significantly higher but FCR was significantly decreased（P<0.05）.The apparent digestibility of crude protein and dry matter were significantly increased（P<0.05）,and B18 group reached the peak.Lipoprotein lipase,hepatic lipase and total lipase in liver were significantly increased（P<0.05）.Digestive enzyme in intestinal has similar trend,moreover,there is no significance difference between B₁₄group and B₁₈ group（P>0.05）.With the increasing lipid level,SOD,CAT and T-AOC activities in three groups showed a trend of first increasing and then decreasing,but there was no significantly difference（P>0.05）.There was no significant difference in GSH-Px activity and MDA.Moreover,GSH-Px activity decreased with increasing lipid levels,while MDA was increased,（P>0.05）.Fatty acid composition in muscle of fish showed a trend of PUFA>SFA>MUFA,although no significance difference was detected among three group（P>0.05）.n-3/n-6 increased in initial stage and then declined.Experiment 3 Three experimental dietary groups were designed for feeding trial:100%fish oil（B_F）,50%fish oil and 50%soybean oil(B_FS)and 100%soybean oil（B_S）.To explore the effect of substitution of dirtary fish oil by soybean oil on growth performance,digestive enzyme activity,antioxidant capacity,lipid utilization.There were no significance differences in the FBW,WGR,SGR,feeding rate（FR）and condition factor（CF）between different feeding groups（P>0.05）.FCR significantly decreased in B_FSS group,however,PER increased significantly（P<0.05）.Crudeprotein content was significantly declined in B_S group,while crude lipid content was significantly increased（P<0.05）,and lipase in intestinal was significantly increased in B_F group（P<0.05）.With the increase of soybean oil substitution ratio the content of DHA and EPA in turbot muscle decreased.Above all,adding bile acid in diet had the effect of promoting growth performance and PER and reducing FCR,furthermore promoting the lipid digestion and absorption,improving theability of fat metabolism,and antioxidant ability.The optimal level of lipid was 18%.Fish oil could be partly substituted by soybean oil,replacement ratio deserves further exploration.