A taste for growth: Rapeseed lecithin improves the feed intake of post-juvenile rainbow trout (Oncorhynchus mykiss)

Feed formulations low in fish meal and fish oil can decrease feed intake and nutrient digestibility. Dietary application of lecithins could improve growth performance and nutrient digestibility; however, knowledge about specific lecithins and their effects in post-juvenile fish is lacking. This study evaluated the effects of a commercially available rapeseed lecithin mixture on growth performance, feed intake, and nutrient digestibility of post-juvenile rainbow trout (77.1 ± 12.1 g). A commercially based diet low in fish meal served as the control, while in the remaining three diets, fish oil was replaced with lecithin by 50%, 100% with lecithin, or 100% with a mixture of equal amounts of lecithin and rapeseed oil. Fish were fed to apparent satiation twice per day for 56 days. At the end of the trial, growth parameters, health parameters, nutrient digestibility, and filet coloration were assessed. Overall growth and feed intake were significantly elevated in all lecithin diets compared with the control group. The nutrient digestibility of all diets containing lecithin was similar to the control, and no differences in health parameters were detected. Filet coloration was significantly improved in diets of 100% fish oil replacement. Rapeseed lecithin can act as a feed attractant in fish meal and fish oil-reduced diets.