Effects of replacement of dietary fish oil by soybean oil on growth performance and hepatosomatic index in Litopenaeus vannamei.

A 42-day feeding experiment was conducted with juvenile Litopenaeus vannamei to evaluate the effects of replacing dietary fish oil with soybean oil on growth performance and hepatosomatic indices.Shrimps in triplicate were respectively fed with four diets:6% fish oil(as control,FO),4.5% fish oil + 1.5% soybean oil(25SO),3% fish oil+3% soybean oil(50SO) and 1.5% fish oil+4.5% soybean oil(75SO).The results indicated that no significant differences(P0.05) were observed among the treatments on mass gain and specific growth rate.The highest survival rate was observed in 75SO group,being significantly higher(P0.05) than that of the control group.75SO group had the lowest feed coefficient,being significantly lower(P0.05) than that of the other groups.Among 25SO,50SO and FO group,hepatosomatic indices existed no significant differences,but that of 75SO group was significantly higher(P0.05) than that of FO group.The results indicated that partly replacing fish oil with soybean oil did not significantly affect growth performance of Litopenaeus vannamei,and the practice was recommended in their diet formulation.According to the two-dimensional relationship constructed between the growth rate and the percentage of fish oil substitution by soybean oil,y=-0.016 8x2+1.207 4x+435.7,the substitution at 35.93% in the diet yielded the best growth(457.39%) in juvenile shrimp.