Effects of C/N Ratio on Water Quality, Growth Performance, Digestive Enzyme Activity and Antioxidant Status of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in Biofloc Based Culture System
Ammar Dilmi, Wahid Refes, Abdellah Meknachi
Abstract
A 62-d trial was conducted to evaluate the effects of different C/N ratios on water quality, growth performance, digestives activity, and antioxidant indicators of tilapia fingerlings in BFT systems. Three biofloc treatments (added molasses) with a C/N ratio of 14 (BFT14), 17 (BFT17), and 20 (BFT20) were tested against control in clear-water, each treatment in triplicate. Four hundred twenty tilapias (24.2±0.1 g) were distributed on 12 tanks of 350 L. The dynamics of water quality parameters showed a shift from a predominantly autotrophic to a predominantly heterotrophic biofloc with an increase in the C/N ratio from 14 to 20. The growth and Feed conversion of tilapia were not significantly different between the control, BFT14, and BFT17 groups. A low weight gain and high FCR were found in the BFT20 treatment (0.61±0.07 and 1.11±0.12 g/d) compared to the control (0.84±0.05 and 1±0.07 g/d). Activities of proteases and alpha-amylase in the liver and digestive tract were similar in all treatments. As a measure of stress, CAT and SOD activities did not differ significantly among the four groups. Overall, it was possible to reduce the C/N ratio to14, without negatively affecting the biofloc development, growth performance, and physiological parameters of juvenile tilapia.