Evaluation of Periphyton as a Food Source for Nile Tilapia (Oreochromis niloticus) Juveniles Fed Reduced Protein Levels in Cages

Abstract

We evaluated the effects of lowering dietary protein levels, in the presence of periphyton substrates, on the performance of Nile tilapia juveniles reared in floating net-cages fixed in an earthen pond. Four wood logs (total surface area of approximately 1 m2) were fixed inside experimental cages as periphyton substrates. Triplicate groups of Nile tilapia (2.37 g average weight) were stocked into the cages (1 m3 each), and fed one of 3 isocaloric (17 MJ kg−1) diets containing 25% (D25, no periphyton), 20% (with periphyton), or 15% crude protein (with periphyton) for 70 days. Tilapia fed the lower protein diets with periphyton performed better (P < 0.05) than those fed the 25% CP control diet. Final fish body composition was not significantly affected by dietary treatments. The diet containing the lowest protein level (D15) with periphyton was the most cost-effective.