Dietary lipid supplementation affects the body fatty acid composition but not the growth of juvenile river chub,Zacco barbata(Regan)

Abstract

A feeding trial was conducted to investigate the effects of dietary lipid level on growth and body composition of juvenile river chub, Zacco barbata (Regan). Juvenile river chub with 0.26 g body weight were given five isoenergetic and isonitrogenous purified diets containing 0–20% lipids in 5% increments for 8 weeks. The dietary lipid source was a 1:1 (w/w) mixture of menhaden fish oil and soybean oil. There was no significant difference on weight gain, feed conversion ratio, or protein efficiency ratio, among fish fed different experimental diets (P > 0.05). Body fat contents of both initial fish and fish fed the diet containing 20% dietary lipid were significantly greater than those fed other diets (P < 0.05). The percentage of total n-3 fatty acids in the body lipids of fish at the beginning of the trial was 12.34%. This value decreased to 3.83% by the end of the trial for fish fed a control diet with no supplemented lipid. Similar trends were observed in linoleic acid contents that were 6.11% and 3.09%, respectively, for initial fish and the fish fed the control diet for 8 weeks. However, the absolute amount of these fatty acids stayed the same in the initial and in the control group. Meanwhile, as dietary lipid level increased, the percentages of these fatty acids in body lipids of fish at the end of the trial also increased.