Plant Protein Substitution for Fishmeal

Concerns for the reduced supply of fishmeal and environmental pollution associated with raceway or cage culture resulted in two studies that evaluated the effects of supplemental lysine in plant protein diets on trout performance, total ammonia nitrogen and soluble phosphorus excretion. Eight diets were fed to triplicate tanks of fish; the diets were formulated to be isonitrogenous and isocaloric. Replacing one-half of the fishmeal with plant protein meals reduced the dietary phosphorus level from 0.9% to 0.6%, which is the requirement for trout. Results indicated that replacing one-half of the fishmeal with plant protein-based diets supplemented with a minimum of 0.4% L-Lysine-HCL had similar weight gains and feed efficiencies compared to fish fed the higher levels of fishmeal during the eight-week study. Fish fed the plant protein-based lysine-supplemented diets discharged less total ammonia nitrogen and soluble phosphorus compared to the fish fed the control diets. These results indicate that reducing dietary protein levels and balancing the intake of essential amino acids with supplemental lysine can support satisfactory rainbow trout performance with significantly reduced amounts of total ammonia nitrogen and phosphorus discharged into the aquatic environment.

Cheng, Z.J. and R.W. hardy. 2003. Dietary lysine in plant protein diets improves rainbow trout performance, water quality. Global Aquaculture Advocate 6(2):56-57.