Effect of Dietary Mixture Containing Azolla and Spirulina Platensis on Physiological, Metabolic, Immunological and Histological Performance of GIFTTilapia (Oreochromis niloticus) Cultured in Lined Ponds

The study aimed to evaluate the effect of Azolla and Spirulina platensis inclution diet on physiological, immunological and histological performance of GIFT Tilapia (Oreochromis niloticus) cultured in lined ponds. With reference to pilot studies conducted in different Azolla and S. platensis inclusion levels, an isonitrogenous (32%) and isocaloric (17 KJ kg-1 DM) diet (15%- Azolla and 3%- S.platensis meal) was formulated to replace fishmeal, while commercial diet was used as control. Animals (5.5 ± 0.04 g) were randomly stocked at a density of 15m^-3 in 100m² lined ponds in all the experimental diets in triplicates. The fishes were fed with experimental diets at 5% of their body weight in two rations throughout the 90 days trial. The results indicated that, water quality parameters (pH, alkalinity, hardness and nitrate), physiological parameters, immunological indices and intestinal villi structure were significantly higher in test diet, while metabolic enzyme activity and liver histology were not influenced by the dietary treatments. Therefore, the study suggests that, partial replacement of fish meal with a combination of Azolla (15%) and S. platensis (3%) meal in semi intensive GIFT tilapia culture is beneficial for the better performance of GIFT tilapia, O. niloticus production.

Keywords: Azolla; Spirulina platensis; GIFT tilapia; Digestive enzymes; Immunity; Carotenoid content