Effect of Dietary Protein Levels on Growth, Body Composition, and Haematology of Tilapia in Biofloc Without Solid Management System

Abstract

This study investigated the effects of varying dietary protein levels on the performance of tilapia reared in biofloc culture system without solid management. Five experimental diets containing crude protein (CP) levels of 32, 28, 24, 20, and 16% were tested in a completely randomized design in triplicate. Tilapia fingerlings (mean initial weight of 40.82 ± 0.38 g) were randomly stocked in biofloc tanks (effective water volume of 300 L) at a stocking density of 65 fish m⁻³. After 13 weeks of feeding trial, significant differences were observed in final weight (g), daily growth (g day⁻¹), feed conversion ratio, and yield (kg m⁻³) (p < 0.05). Water quality parameters remained unaffected by dietary treatments (p > 0.5). Notably, fish fed with diets containing 32%, 28%, and 24% CP demonstrated similar growth performance. Based on weight gain, a linear response plateau model estimated the minimal dietary CP level of 24.5%. Dietary CP levels altered visceral index (p < 0.05), but not visceral fat index, hepatosomatic index, or spleen somatic index (p > 0.05). Similarly, dietary CP levels did not significantly affect the fish composition (p > 0.05) and the haematological parameters of the experimental fish (p > 0.05). These results suggest that dietary protein in a small-scale biofloc system can be reduced from 32% to 24.5% without compromising fish health. However, appropriate solid management in biofloc systems is recommended to ensure optimal growth of fish.