The Effect of Replacement of Fish Oil by Soybean or Canola Oils With L-Carnitine Supplement on Growth Performance of Rainbow Trout, Oncorhynchus mykiss

The sources of fish oil for use in aquaculture is limited and different oil sources vary in fatty acid composition. The main objective of this experiment was to determine the effects of plant oil sources such as soybean and canola oils with or without L-carnitine supplement on some blood biochemical parameters and growth performance of fingerlings rainbow trout. In 3×2 factorial experimental design, 180 rainbow trout with 28±2 g initial body weight were randomly divided into six groups with three replicates and fed two times a day at ad libitum by dietary treatments during 10 weeks. The experimental diets contained three dietary oil sources such as fish, soybean and canola oil; and two supplemental dietaries L- carnitine levels (0 and 1 g.kg-1). Feed conversion ratio, specific growth rate, feed intake, body weight gain and blood biochemical parameters of fish such as albumin, total protein, triglyceride, cholesterol and high-density lipoprotein (HDL) were measured at the end of the experiment. Replacement of fish oil by soybean and canola oil had no significant effect on growth performance such as body weight gain, feed intake, feed conversion ratio, specific growth rate, hepatosomatic index, carcass weight and condition factor of fish. L-carnitine supplement significantly improved weight gain and feed conversion ratio and increased condition factor of fish (P<0.05). Soybean oil significantly increased cholesterol and triglyceride level, and canola oil decreased HDL and globulin level in blood serum of fish (P<0.05). Results of this study showed that fish oil could be wholly replaced by soybean or canola oil in the diet of rainbow trout and also physiological responses and growth performance of fish to carnitine supplement were affected by dietary oil sources.