Performance of rainbow trout fry fed supplemental soy lecithin and choline

Three feeding experiments were conducted with early‐feeding fry of rainbow trout (Oncorhynchus mykiss; initial mean weight, 0.10–0.12 g) to determine their need for lecithin contained in soy lecithin (SL), with and without supplemental choline. The source of assay protein was an isoelectric form (RP 100) of isolated soy protein (ISP) in experiment 1, a sodium protein ISP (RP 101) in experiment 2, and an ether‐extracted herring meal in expenment 3. Duration of the feeding trials was 20 weeks for experiment 1 and 16 weeks for experiments 2 and 3. Analysis of variance showed that supplemental SL and choline each increased body weight gain, survival, and body fat, and improved feed conversion (amount fed/weight gain). The extent of beneficial effects varied with type of diet fed. Fish fed either of the ISPs needed at least 4% supplemental SL, either with or without 0.3% choline, for highest survival, but survival of all fish fed extracted herring meal was high. Although choline alone enhanced growth, at least 4% SL, either with or without choline, was necessary for maximum growth.