Effect of dietary spirulina supplements on growth, haematological factors and survival of Oreochromis shiranus challenged with Aeromonas hydrophila

A study was conducted to determine the effect of spirulina (Arthrospira platensis) on growth performance and resistance of Oreochromis shiranus to Aeromonas hydrophila infection. Four diets containing 0, 3.5, 7.0 and 10.5 g spirulina/kg of the diet were fed to O. shiranus fingerlings twice daily for 10 weeks. After the feeding trial, fish from each treatment were divided into two groups. The first group was challenged with 0.1 ml dose of 5x105cells/ ml of A. hydrophila while the second group was given 0.1 ml of saline solution as a control and observed for 10 days. Fish fed with 7g spirulina/kg of basal diet recorded the highest growth in terms of weight gain, gain in length and specific growth rate. The highest mean total feed intake for the entire experimental period was observed in fish fed with 7g spirulina/ kg. Fish in the control treatment had the highest Feed Conversion Ratio (FCR) while Treatment 3 (7g spirulina/kg) recorded the least FCR. The control treatment had the least Protein Efficiency Ratio (PER) while Treatment 3 (7g spirulina/kg) recorded the highest PER. The lowest mean survival rate was observed in the control diet. Hematological parameter of the fish increased as spirulina supplement levels increased. Cumulative mortality rate for the fish fed with the control diet was significantly higher (66.67%) than those of fish fed diets 2–4 (P < 0.05). The results of the present study indicate that incorporation of spirulina into the formulated diet promote immune responses in O. shiranus thereby increasing the resistance of the fish to A.hydrophila infection, hence reducing fish mortality and contributing to economic benefits.