Effect of oil source and dietary supplements of L-carnitine and ractopamine on growth performance and some blood biochemical parameters of rainbow trout, Oncorhynchus mykiss

An experiment was conducted to study the effects of oil source, L- carnitine and ractopamine supplements on growth performance and blood biochemical parameters of rainbow trout. With 2×2×2 factorial experimental design, 288 fish with 90 ±5 g initial weight were randomly distributed to 32 fiber glass thanks and fed two times a day at ad libitum by eight dietary treatments during 8 weeks. The experimental diets were containing two supplemental dietaries L- carnitine levels (0 and 1 g.kg-1), two levels of ractopamine (0 and 10 mg.kg-1) and two dietary oil sources (fish and soybean oil). Feed conversion ratio (FCR), specific growth rate (SGR), feed intake, body weight gain and biochemical parameter of blood serum in fish such as albumin, total protein, triglyceride, cholesterol and high density lipoprotein (HDL) were measured at the end of experiment. Results showed that feed conversion ratio of fish was not affected by dietary oil sources and ractopamanie supplements but addition of L- carnitine to diet reduced it significantly. Addition of L-carnitine and ractopamine to diet which contain fish oil improved significantly FCR of fish. Fish oil increased fish SGR and its highest level was seen at fish oil plus ractopamine dietary treatment. Feed intake was affected by fish oil and L- carnitine supplement which is increased and reduced it, respectively. Addition of L- carnitine to diet containing fish oil with ractopamine, significantly reduced feed intake of fish. Body weight gain of fish were not affected by dietary oil sources, L-carnitine and ractopmanine supplement however, addition of ractopamine to diet containing fish oil improved it. Ractopamine supplement significantly reduced level of triglyceride and L-carnitine increased albumin and HDL of blood serum of fish. Interaction between oil sources and addition of L- carnitine and ractopamine supplements were seen on biochemical blood serum of fish except HDL. The highest level of albumin and triglyceride in blood serum were seen in fish fed by soybean oil plus L- carnitine, and also the highest level of total protein and globulin in serum were in fish fed by soybean oil plus ractopamine. Overall, results of this experiment showed that physiological and growth responses of rainbow trout to dietary L- carnitine and ractopamine supplements were affected by dietary oil sources.