Effects of microalgae‐added diets on growth performance and meat composition of tilapia (Oreochromis mossambicus)

Two floating diets and one sinking diet were prepared for tilapia with local ingredients by extrusion or steam‐pelleting methods. Indoor and outdoor feeding trials were conducted to evaluate their effects on growth performance and quality of tilapia products. Local ingredients included defatted Haematococcus and Spirulina by‐products from Hawaii. The three diets, plus a commercial feed, were each assigned to three replicate tanks, and each tank (120 L) was stocked with 12 juvenile tilapia in an 8‐week indoor trial. The results showed that (1) the floating diet had significantly (P < 0.05) higher weight growth than the sinking diet; (2) increased inclusion of local microalgae by‐product (defatted Haematococcus) in floating diet from 12% to 24% significantly (P < 0.05) decreased tilapia weight growth; and (3) the three microalgae‐added diets obtained higher (P < 0.05) weight growth than the commercial feed, although they contained lower protein (36.9% to 37.7%) and lipid (7.1% to 8.1%) than the commercial feed (42.3%; 8.6%). The floating diet (containing 12% microalgae) and the commercial feed were also tested in outdoor green water tanks, simulating the commercial production conditions of local tilapia farms. Each diet had three replicate tanks (1200 L) stocked with 100 juvenile tilapia. The 12‐week trial showed that the local diet had significantly (P < 0.05) lower growth (12.0 g week^?1) than the commercial feed (14.8 g week^?1). All tilapia meat products were measured with low n‐3 fatty acid contents. These results provide important information for feed formulation and production using local ingredients for tilapia.