Multiple amino acid supplementations to reduce dietary protein in plant-based rainbow trout, Oncorhynchus mykiss, feeds

Reducing dietary protein in trout feeds will reduce production costs if growth performance can be maintained. A study was conducted to determine if balancing plant-based diets oil all available amino acid basis to the profile Of trout muscle would result in equal performance with a reduction in total protein level. The diets were formulated to contain either 45 or 35% intact crude protein (45CP and 35CP diets, respectively). To these basal diets, lysine. methionine, threonine and glycine were Supplemented to be equivalent to 450 g/kg protein from rainbow trout muscle (45AA and 35AA, respectively) oil all available amino acid basis. A fifth diet was formulated to contain 35% crude protein from plant proteins and Supplemented as for the 35AA diet but only with lysine, methionine and threonine (35AA-Gly), The diets were fed to apparent satiation to triplicate ranks of 25, 20 g rainbow trout for a period of 12-weeks. Amino acid supplementation improved weight gain by 11% in the 45AA diet over the 45CP diet and by 11.6 and 15% in the 35AA and 35AA-Gly diets relative to the 35CP diet. Feed conversion ratio was poorest for the 35CP diet compared to other treatments. Protein retention efficiencies were improved in the 35AA and 35AA-Gly dietary treatments compared to the 45CP treatment. Intraperitoneal fat ratio decreased with amino acid Supplementation at both crude protein levels. Muscle ratio increased by 10% when amino acids were Supplemented to the 45CP diet and by an average of 13.6% when amino acids were supplemented to the 35CP diet. Amino acid Supplementation reduced the retention efficiency of lysine with no affects on methionine and threonine. Retention efficiencies of isoleucine and leucine were increased by amino acid supplementation at both basal protein levels. Glycine Supplementation had no beneficial effects on fish performance. In conclusion, dietary Crude protein content of plant-based diets for rainbow trout call be reduced from 46 to 41.5% by supplementing lysine, methionine, and threonine with no reduction in growth and an improvement in protein retention efficiency and muscle ratio. Published by Elsevier B.V.