Fish meal has been an important source of protein in fish diets because of its high protein quality and palatability.
However, fish meal is very expensive and can substantially increase feed costs. Since fish meal is used as the main
protein source in aqua-feeds, recent researches have been concentrated on the partial or total replacement of fish
meal with less expensive and locally available protein sources for tilapia [8]. Total or partial replacement of fish
meal with less expensive animal protein, such as poultry by-product meal (PBM) may help to reduce feed costs,
although these sources may be lower in digestibility, palatability and essential amino acids [9, 10 and11].