First‐feeding Atlantic salmon (Salmo salar) were fed different levels (0, 2, 4, 6, and 8% of diet) of feed‐grade lecithin with and without 0.3% supplemental choline in a diet containing a sodium proteinate form of autoclaved isolated soybean protein. After 14 weeks at 9.2°C, Atlantic salmon fed 6% lecithin with or without added choline had gained the most weight. Fish fed supplemental choline without lecithin gained significantly more weight (P ≤ 0.05) than did fish fed the basal diet, but choline did not increase weight gain at any level of lecithin. Feed conversion (weight fed/weight gain) improved with increasing lecithin up to 4% and improved even more for fish fed 6% lecithin and 0.3% choline. Only 4% lecithin with or without choline was needed to yield the highest concentration of body fat, but carcass dry matter was highest and ash and protein were lowest in fry fed 8% lecithin alone or 6% lecithin and 0.3% choline. Neither lecithin nor choline influenced mortality, which was low in all groups. Results indicate that 6% dietary feed‐grade lecithin promotes maximum weight gain by swim‐up Atlantic salmon fry fed autoclaved isolated soybean protein as the primary protein.
