Can cyclical food restriction support growth of juvenile Nile tilapia (Oreochromis niloticus) in brackish water biofloc?

The effects of cyclical feeding restriction (3, 4, 5, 6, and 7 days of feeding per week) on the performance of juvenile Nile tilapia (Oreochromis niloticus) in a biofloc technology system (BFT) were evaluated in this study for 77 days. Fifteen experimental units (400L) with temperature control (mean 28.2 °C) randomly distributed 1500 fish (0.42 ± 0.02 g). Fish were fed commercial feed (46.7 g of crude protein and 4475.5 kcal kg−1 of gross energy) up to satiation. Feeding cycles with different restrictions (p < 0.05) influenced animal growth but not survival and final density (p > 0.05), which remained around 94% and 235 fish.m−3, respectively. Juveniles fed 6 days a week showed 1.25 of feeding efficiency, while animals fed 3 days a week (more restricted) showed hyperphagia but did not exhibit compensatory growth. Changes in the morphology of hepatocytes (presence of vacuoles, displacement of the nucleus to the periphery, and fatty degeneration) were observed with an increase in feeding days, and a high degree of hepatic steatosis (p < 0.05). Water quality parameters remained within acceptable limits for the species and system operation. Feeding regimes influenced the characteristics of bioflocs (total suspended solids and porosity) and the abundance of microorganisms (p < 0.05). Nutritionally, less restricted diets (6 and 7 days of feeding per week) produced more protein (38.3 and 40.6% CP) and energy bioflocs (2252.8 and 2313 kcal.kg−1) (p < 0.05), while protein, lipid, and body energy were significantly lower (p < 0.05) with the more restricted diet. The composition of microorganisms was influenced by the feeding regimes (p < 0.05). Results demonstrated that the occurrence of total compensatory growth (6 days of feeding per week) represents an economic advantage with a reduction of 26.8% of feed and greater profitability in the unitary commercialization of tilapia juveniles. [ABSTRACT FROM AUTHOR]