Carbon sources affect water quality and haemato-biochemical responses of Labeo rohita in zero-water exchange biofloc system

Biofloc technology degrades waste into useful resources exploiting microbes and can be used in zero-water exchange systems. To study the effect of different biofloc systems on haematological and metabolic response of Labeo rohita fingerlings, a 60-days experiment was conducted using four long lasting carbon sources. Seven hundred and fifty fingerlings having mean weight of 4.80 +/- 0.12 g were randomly distributed into 15 tanks (n = 50 per tank). Five experimental groups were set in triplicate; T1 (Tapioca), T2 (Wheat), T3 (Corn) T4 (Sugar bagasse) and control (clear water). In-situ biofloc was developed in 300 L fibre-reinforced plastic (FRP) tanks and a C/N ratio of 15 was maintained. Water quality variables indicated ammonia immobilization by heterotrophic bacteria, as the dominant mechanism for the removal of toxic-nitrogenous compounds in the biofloc systems. Results exhibited significantly higher floc volume (53.33 +/- 7.88 ml/L), haemoglobin content (6.61 +/- 0.03 g/dl) and total leucocyte count (109.66 +/- 0.06 thousand cells/mm(3)) in tapioca biofloc system. Furthermore, the digestive and anti-oxidative enzymes activities were also significantly higher in tapioca biofloc system. The lactate dehydrogenase and malate dehydrogenase enzyme assays showed a decreased level in tapioca biofloc system as compared with other biofloc systems and control group. Our observations indicate that tapioca biofloc system could improve the water quality, haematological and anti-stress responses of L. rohita fingerlings in biofloc systems and thus can effectively replace other carbohydrate sources for the biofloc system.