| Juvenile Rhynchocypris lagowskii Dybowski with initial weight(5.30±0.01)g were assigned to one of five treatment groups and fed one of five isonitrogenous(crude protein was 36.0%)formulated diets containing 3.38%(CK),5.34%,7.30%,9.26% and 11.22% lipid for 8 weeks.Using fish meal,soybean,rapeseed meal and cottonseed meal as protein source,fish oil as fat source.The effects of different dietary lipid levels on the growth performance,antioxidantic activities and fatty acid composition of Rhynchocypris lagowskii Dybowski were evaluated.The results showed that:1.Effects of dietary lipid levels on the growth performance,feed utilization,and nutritional compositions of Rhynchocypris lagowskii DybowskiWith the increase of dietary lipid levels,the body weight,weight gain rate,feed efficiency ratio and protein efficiency ratio increased first and then decreased.When the feed lipid level were 7.30%,9.26% and 11.22%,weight gain rate,feed efficiency ratio and protein efficiency ratio were significantly higher than those in 3.38% and 5.34% groups(P<0.05).When the feed lipid level was 7.30%,specific growth rate was significantly higher than that in 3.38% and 5.34% groups(P<0.05),but there was no significant differences in specific growth rate in 7.30%,9.26% or 11.22% groups(P>0.05).By the polyline regression model,when weight gain rate has reached the maximum,the most suitable lipid level was 7.60%.When specific growth rate has reached the maximum,the most suitable lipid level was 7.77%.In this experiment,when the feed lipid level were 7.30%,9.26% and 11.22%,crude lipid was significantly higher than that in 3.38% and 5.34% groups(P<0.05).There was no significant differences in moisture,crude protein and crude ash when the feed lipid levels was different(P>0.05).2.Effects of dietary lipid levels on the activity of digestive enzyme of Rhynchocypris lagowskii DybowskiIn this experiment,when the feed lipid level were 5.34%,7.30% and 9.26%,there was no significant differences in the activity of protease than that in control group in foregut and midgut(P>0.05),when the feed lipid level was 11.22%,the activity of protease was significantly lower than that in control group in foregut and midgut(P<0.05).There was no significant differences in the activity of protease in hindgut and hepatopancreas(P>0.05).With the increase of dietary lipid levels,the activity of lipase increased first and then decreased in foregut,midgut,hindgut and hepatopancreas,when the feed lipid level was 7.30%,the activity of lipase in foregut and midgut has reached the maximum,and was significantly higher than that in other groups(P<0.05).There was no significant differences in the activity of lipase in hindgut and hepatopancreas(P>0.05).In this experiment,there was no significant differences in the activity of amylase in foregut,midgut,hindgut and hepatopancreas when the feed lipid levels was different(P>0.05).3.Effects of dietary lipid levels on the antioxidantic activities of Rhynchocypris lagowskii DybowskiIn this experiment,the content of MDA increased with the increase of dietary lipid levels,and was significantly higher than that in control group when the feed lipid level were 5.34%,7.30%,9.26% and 11.22%(P<0.05).The activity of SOD increased first and then decreased and was significantly higher than that in control group when the feed lipid level were 7.30% and 9.26%(P<0.05).With the increase of dietary lipid levels,the activity of CAT,GRAC,GSH-PX and GST in hepatopancreas increased,but there was no significant differences in each group(P>0.05).4.Effects of dietary lipid levels on the lipid metabolism enzyme of Rhynchocypris lagowskii DybowskiIn this experiment,with the increase of dietary lipid levels,the activity of LPL,HL and GE increased.When the feed lipid level were 7.30%,9.26% and 11.22%,the activity of LPL and GE were significantly higher than that in 3.38% and 5.34% groups(P<0.05).With the increase of dietary lipid levels,the activity of MDH decreased.When the feed lipid level were 5.34%,7.30%,9.26% and 11.22%,the activity of MDH was significantly higher than that in control group(P<0.05).5.Effects of dietary lipid levels on the fatty acid composition of Rhynchocypris lagowskii DybowskiIn this experiment,with the increase of dietary lipid levels,the proportion of SFA in muscle decreased,but the ∑n-3/∑n-6 index increased,and it was significantly higher than that in control group when the feed lipid level were 9.26% and 11.22%(P<0.05),it ascended from 2.16% to 3.98%.the proportion of PUFA decreased first and then increased,but there was no significant differences in each group(P>0.05),it ascended from 22.63% to 24.81%.With the increase of dietary lipid levels,the proportion of SFA in hepatopancreas decreased,when the feed lipid level were 5.34%,7.30%,9.26% and 11.22%,the proportion of SFA in hepatopancreas was significantly lower than that in control group(P<0.05),the proportion of n-3 PUFA in hepatopancreas increased with the increase of dietary lipid levels.The proportion of ∑n-3 in hepatopancreas was significantly higher than that in control group when the feed lipid level were 7.30%,9.26% and 11.22%,but there was no significant differences in the proportion of ∑n-6 and ∑n-9 in each group(P>0.05).With the increase of dietary lipid levels,the proportion of SFA in abdomen decreased,and it was significantly lower than that in control group(P<0.05).When the feed lipid level were 9.26% and 11.22%,the proportion of ∑n-3 in abdomen first increased and then decreased,when the feed lipid level were 7.30%,9.26% and 11.22%,the proportion of ∑n-3 in abdomen was significantly higher than that in 3.38% and 5.34% groups(P<0.05).When the feed lipid level were 9.26% and 11.22%,the proportion of ∑n-6 in abdomen was significantly lower than that in control group(P<0.05).There was no significant differences in the proportion of ∑n-9 and ∑n-3/∑n-6 index in each group(P>0.05).The proportion of MUFA was significantly higher than that in control group when the feed lipid level were 7.30%,9.26% and 11.22%(P<0.05).Comprehensive analysis of the above factors,the suitable lipid level in the diet can improve the growth,activity of digestive enzyme,antioxidantic activities and lipid metabolism enzyme of Rhynchocypris lagowski Dybowski.In the formulated diets of juvenile Rhynchocypris lagowski Dybowski,the most suitable lipid level is 7.30% to 9.26%. |
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