Crude protein levels in diets for two growth stages of Nile tilapia (Oreochromis niloticus) in a biofloc system

Abstract

Biofloc technology (BFT) provides an additional feed source for aquatic organisms through the conversion of waste in microbial flocs. Because of this, the suitable protein level in a diet for animals in this system could be different from those in conventional systems. Our objective was to determine the suitable protein level in the diet of Nile tilapia juveniles reared with BFT. Two experiments were carried out with tilapia weighing~10 g (first experiment) and about 50 g (second experiment) during 61 and 98 days respectively. Five crude protein (CP) levels (within 17% and 33%) were tested. The increment of CP resulted in a reduction in dissolved oxygen, pH, alkalinity and an increase in dissolved phosphorus, total suspended solids and total ammonium nitrogen. The crude protein level had a significant effect (p < 0.05) on animal performance. The linear response plateau model was the best fit for the final weight and weight gain data in the two growth phases. In conclusion, tilapia juveniles of 10-60 g and 60-230 g in biofloc can be fed on diets with 28% of CP (26% of digestible protein) and 22% CP (20% of digestible protein) respectively. K E Y W O R D Sbiofloc technology, growth performance, Nile tilapia, nutrition

Dietary protein reduction for Nile tilapia fingerlings reared in biofloc technology

“…Variations on biofloc composition were related to the different BFT trials. Comparing other experiments that evaluated CP in BFT, the results of the present study were higher than 37.93 and 38.41% CP (Azim & Little, ) and 15.09 to 20.31% CP (Silva et al, ). According to Crab et al (), different carbon sources and ratios influence the CP content of biofloc, which can reach 28–58%.…”

“…The values obtained in this experiment from SS and TSS were within the recommended limits for BFT (Avnimelech, ). However, Azim and Little () and Silva et al () observed TSS reaching up to 1,000 mg/L in different studies with tilapia fed different CP concentrations.…”

“…CP and was superior to that analyzed by Silva et al (2018), which ranged from 15.09 to 20.31% CP; this could complement any protein deficiency, as biofloc can supplement up to 50% of the protein requirement of tilapia (Avnimelech, 2007). Due to the variation of the nutritional content of biofloc, analysis of the proximal composition of biofloc and diet is essential, since this complementary protein source influences the reduction of diet protein content.…”

“…Silva et al () evaluated different CP levels (18–33%) for tilapia in BFT, and estimated 28% CP (26% DP) as the optimal level for the growth of tilapia (10–60 g). These results were close to those obtained in the present study with Nile tilapia fingerlings (6–30 g).…”

“…On the other hand, Mansour and Esteban (2017) observed the best tilapia performance (48 g) when they were fed diets with 20% CP in BFT, compared to tilapia fed with 30% CP in the system without BFT. Silva et al (2018) evaluated different CP levels (18-33%) for tilapia in BFT, and estimated 28% CP (26% DP)…”