Effect of dietary lipid level on body index,lipid deposition and lipid metabolic enzyme activities of juvenileOnychostoma sima

Abstract

This experiment was conducted to study the effect of dietary lipid level on the body index,lipid deposition and lipid metabolic enzyme activities of juvenile Onychostoma sima.We randomly assigned fish(n=900)with average initial body weight of(0.78±0.05)g into 6 groups consisting of 3 replicates that each replicate was 50 fish.Six isonitrogenous and isoenergetic diets(40% CP and 16.30 MJ/kg GE)were formulated containing 0(control group),2%,4%,6%,8%or 10% soybean oil respectively,Those actual lipid level was 2.83%,4.52%,6.68%,9.14%,11.35% and 14.07%,respectively.The experiment lasted for 60 days.The results showed that the condition factor(CF)of Onychostoma sima initially increased with increasing lipid levels,but then decreased,the CF was highest(2.64%)when the dietary lipid level was 9.14%,but there was no significant differences when lipid level were 6.68%-14.07%,(P0.05).The hepatosomatic index(HSI)increased with increasing dietary lipid levels(P0.05),while viscerosomatic index(VSI)had no significant differences(P0.05).The crude lipid content of muscle and liver were easily affected by dietary lipid levels,and the crude lipid content of muscle and liver increased with increasing dietary lipid levels.There was no significant effect of dietary lipid level on nitrogen gain(P0.05),energy gain was highest when the dietary lipid level was 14.07%,at the same time,the nitrogen and energy retention initially increased with increasing lipid levels,but then decreased,those were highest when the dietary lipid level was 11.35% and 9.14% respectively.Lipid gain of Onychostoma sima increased with increasing dietary lipid levels,but the lipid retention decreased(P0.05).The activities of intestinal lipase initially increased with increasing lipid levels,but then decreased,and the activities of lipoprotein lipase,hepatic lipase and total lipase first increased,then decreased as the level of dietary lipid increased,those were all highest(296.03 U/g,30.59 U/g,34.28 U/g and 64.87 U/g respectively)when the dietary lipid level was 9.14%.At the same time,fatty acid synthetetase(FAS)decreased with the increase of contents.Results of above show that suitable dietary lipid level could improve the utilization rate of feed nutrients and reduce body lipid deposition,but when dietary lipid level reaches or exceeds 11.35%,the lipid deposition in liver would increase,which is bad for health and growth of Onychostoma sima.