| Fish meal,soybean,rapeseed meal and cottonseed meal were used as protein source,whereas fish oil and corn oil were used as fat source.Phoxinus lagowskii Dybowski with initial weight(7.64±0.04g)were assigned five groups fed with isonitrogenous(crude protein was 36.0 %)and 6.0 % lipid formulated diets containing 0.0 %,10.0 %,16.0 %,22.0 %,or 28.0 % carbohydrate for 8 weeks in temperature control aquaculture system to explore the effects of different dietary carbohydrate levels on growth,immune and related metabolic enzyme activity.These results showed that:1.The effects of different dietary carbohydrate levels on growth,feed utilization and muscle composition of Rhynchocypris lagowski DybowskiIn the current study,with the increase of carbohydrate level,body weight,weight gain rate,feed efficiency ratio,specific growth rate and protein efficiency ratio were increased and then decreased,when the feed carbohydrate level was 16.0 %,body weight,weight gain rate and feed efficiency ratio were significantly higher than that in control group(P<0.05).By the polyline regression model,when weight gain rate has reached the maximum,the most suitable carbohydrate level was 15.84 %.By the polyline regression model,when specific growth rate has reached the maximum,the most suitable carbohydrate level was 15.94 %.When the feed carbohydrate level was 28.0 %,the crude fat content was significantly higher than that in control group(P<0.05).When the feed carbohydrate level were 10.0 % and 16.0 %,the crude protein content showed no significant difference with the control group(P>0.05).When the feed carbohydrate level were 22.0 % and 28.0 %,the crude protein content was significantly lower than that in control group(P<0.05).Moisture and ash content showed no significant difference in every group.2.Effects of dietary carbohydrate levels on non-specific immunity indexes of Phoxinus lagowskii DybowskiIn the current study,with the increase of carbohydrate level,the activity of SOD decreased,and it was significantly lower than that in control group when the feed carbohydrate level were 10.0 %,16.0 %,22.0 % and 28.0 %(P<0.05).With the increase of carbohydrate level,the activities of AKP,ACP and LZM increased and then decreased.When the feed carbohydrate level were 16.0 %,22.0 % and 28.0 %,the activities of AKP and ACP were significantly higher than those in control group(P<0.05).When the feed carbohydrate level were 22.0 % and 28.0 %,the activity of LZM in hepatopancreas was significantly higher than that in control group(P<0.05),10.0 % and 16.0 % groups showed no significant difference with the control group.3.Effects of dietary carbohydrate levels on digestive enzymes of Phoxinus lagowskii DybowskiIn the current study,with the increase of dietary carbohydrate levels,the activities of protease,amylase and lipase in hepatopancreas,foregut,midgut and hindgut were increased firstly and then decreased.Hepatopancreas protease activities,group10.0%,16.0% and 22.0% was significantly higher than the control group(P<0.05),while the group 28.0% was significantly lower than the control group(P<0.05);the protease activities in foregut,midgut and hindgut of group 10.0%,16.0%,22.0% and 28.0% were significantly higher than control group(P<0.05).The amylase activities of hepatopancreas in group10% and 16% was significantly higher than the control group(P<0.05),while group 22.0% and 28.0% were significantly lower than the control group(P<0.05);the amylase activities in foregut and hindgut of group 22.0% reached the maximum,and group 10.0%,16.0%,22.0% and 28.0% was significantly higher than the control group(P<0.05).The amylase activity in the midgut of group 16.0% reached the maximum,and group 16.0% and 22.0% were significantly higher than those in the control group(P<0.05),but the difference between group 10.0% and the control group was not significant(P>0.05),and group 28.0% was significantly lower than that of the control group(P<0.05).The lipase activities in hepatopancreas,foregut,midgut and hindgut of group 10.0%,16.0%,22.0% and 28.0% were significantly higher than the control group(P<0.05).4.Effects of dietary carbohydrate levels on carbohydrate metabolic enzymes of Phoxinus lagowskii DybowskiIn the current study,with the increase of the dietary carbohydrate level,the activities of hexokinase,pyruvate kinase,fructose 1,6-bisphosphatase in hepatopancreas and the original content of glycogen were firstly increased and then decreased.When dietary carbohydrate levels were 16.0% and 22.0%,hexokinase activities in hepatopancreas were significantly higher than the control group(P<0.05),while hexokinase activities in hepatopancreas in group 10.0% and 28.0% of were no significant difference with control group(P>0.05);pyruvate kinase activities of 16.0%,22.0% and 28.0% groups were significantly higher than that of the control group(P<0.05),while group 10.0% and the control group had no significant difference(P>0.05);fructose 1,6-bisphosphatase activities of group 16.0% and 22.0% were significantly higher than those in control group(P<0.05),while group 10.0% and 28.0% and the control group had no significant difference(P>0.05);the original content of glycogen of group 22.0% and 28.0% were significantly higher than that of the control group(P<0.05),while group 10.0% and 22.0% and the control group had no significant difference(P>0.05).According to the above results,the suitable carbohydrate in feed can improve the growth performance,immunity,digestive enzymes activities and carbohydrate metabolic enzymes activies of of Rhynchocypris lagowski Dybowski.In the formulated diets of Rhynchocypris lagowski Dybowski,the most suitable carbohydrate level is 16.0% to 22.0%. |
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