Effects of Spirulina sp. on growth performance and antibody levels in hybrid catfish, Clarias macrocephalus x Clarias gariepinus (Burchell)

A 8-wk feeding trial was carried out for hybrid catfish with an initial average weight of 7 g in 235-l glass tanks attached to closed-recirculating system with 0.8 l/min flow rate. Feeds containing varying percentages of dry Spirulina sp. 0, 5, 10, 15, 20, 25 and 30% were tested with three replications for each treatment. All the feeds were formulated to contain dietary requirement for the catfish i.e. 30% protein, 7% fat and 360 kcal gross energy/ 100 g feed. The results showed that the feed with 10% Spirulina sp. achieved the best performance on weight gain, specific growth rate, feed conversion ratio, apparent net protein utilization and development of antibody levels against bacteria Aeromonas hydrophila. The total carotenoid contents in fish flesh increased with the level of Spirulina sp. supplemented. The supplementation of Spirulina sp. resulted in no changes of blood parameters or histology.