The impact of stocking density and dietary carbon sources on the growth, oxidative status and stress markers of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions

Abstract

The present study investigated the impact of stocking density and dietary carbon sources on the growth, oxidative status and stress markers of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions. Six groups were established at three levels of stocking densities [20, 40 and 60 fish (50.47 ± 0.05 g) per m3] and fed the basal diet without carbon sources or with broken rice flour (BRF) or broken wheat grain flour (BWGF) in biofloc units. Water quality [pH, biological oxygen demand (BOD), Total ammonia-nitrogen (TAN), and nitrite-nitrogen (NO2)] values were increased significantly (P < 0.05) as the density increased and recorded the highest values in group (60 fish per m3) while dissolved oxygen decreased. Biofloc volume and bacterial counts were significantly (P < 0.05) lower in 20 fish m−3 and the highest values were in 40 fish per m3. Significantly increased growth and feed utilization were recorded in 40 fish per m3 fed with BRF. The lipid content lowered significantly (P < 0.05) in 60 fish m-3 group. Red blood cells count, hemoglobin and hematocrit values were reduced in fish stocked in high density while alanine transaminase (ALT) and aspartate transaminase (AST) increased in fish reared in low density. Glucose, cortisol, catalase and superoxide dismutase increased in fish reared at 20 fish m-3 and fed the basal diet. Thus, using of BRF for fish reared at 40 fish per m3 promotes growth and health status of Nile tilapia cultured in a biofloc system. Keywords: Biofloc, Carbon source, Growth performance, Stress markers, Nile tilapia, Stocking density