Evaluation of Ethanolic Extract of Red Seaweed (Gracilariopsis lemaneiformis) on Growth and Haematological Parameters of Nile Tilapia (Oreochromis niloticus)

Seaweed is multicellular marine macroalgae that enhances the immunity of aquatic organisms. The study was designed to assess the ethanolic extract (EtOH) extracted from red seaweed (Gracilariopsis lemaneiformis) on Nile tilapia (Oreochromis niloticus) to evaluate growth, immunity and haematological parameters. The EtOH was applied with fish feed in four treatments such as T1-control (0% EtOH), T2 (5% w/v EtOH), T3 (10% w/v EtOH) and T4 (15% w/v EtOH) each with three replicates. The initial average weight of the fish was 17.53 ± 2.1 g. Results showed that the growth increased gradually with the percentage of red seaweed extract, whereas the mean weight gain was found significantly higher in T4 (51.5 ± 4.2) than in the control. The specific growth rate (%) and survival rate (%) were found higher in T4 at the lowest FCR compared to other treatments (p < 0.05). The blood haemoglobin level of Nile tilapia was higher in T4 (11.5 g/dL) and lowest recorded in T1 (7.5 g/dL). However, the level of blood glucose interacted inversely with blood haemoglobin. The plasma protein level was also varied among the treatments (p > 0.05). The blood parameters, refractive index (RI) and spleen somatic index (SSI) were significantly different among the treatments. The RI of blood plasma and SSI were found to be better in T4 treatment. The research indicated that red seaweed extracts significantly enhanced the growth and boosted the immunity level of Nile tilapia.