EFFECTS OF LOCAL-MADE DIETS ON THE GROWTH AND MEAT COMPOSITION OF TILAPIA Oreochromis mossambicus

As commercial feeds become more expensive due to increases in transportation costs, the demand for local-made feeds are increasing. In Hawaii and the Pacific Islands, many agricultural and fishery byproducts are available to be used as feed ingredients. A microalgal byproduct (defatted Haematococcus - or DH) can act as protein ingredient to replace fish meal in aquatic feeds. This research tested algae-added floating and sinking diets on growth, survival and nutritional composition of meat products of tilapia (O. mossambicus).

Three diets were formulated with around 37% crude protein using locally available ingredients: Diet-1 and Diet-2 included 12% and 24% DH, respectively and were processed as floating pellets by extruder method, and Diet-3 had the same feed formula as Diet-1, but was processed as sinking pellets by the triple-pass method. An indoor trial was conducted on juvenile tilapia for the three diets and a commercial feed. Ten fish were maintained in three, black 150L tanks for each of the diets and fed twice daily. Air stones were supplied, and daily siphoning to remove uneaten feed and feces was performed to obtain 100% fish survival.

Diet-1 obtained significantly higher final weight gain (65.09 g) and specific growth rates (2.00 %/day) than those of Diet-2 (53.82 g, 1.81 %/day; Table 1). This suggests that 24% DH addition retarded animal growth, probably due to high fiber content from the high DH inclusion in Diet-2. The floating diet (Diet-1) showed significantly higher growth rates (5.42 g/wk) than sinking Diet-3 (4.29 g/wk), indicating tilapia prefer to eat floating pellets.  Growth performance for the algae-added Diet-1 was also better than floating commercial feed (3.91 g/wk), despite the higher protein content of commercial feed (42.3 %).  Nutritional composition of tested diets and meat products, including proximate content, amino acid and fatty acid profiles, were also analyzed.

The results of this study indicate that local-made diets could be cost-effective, when produced with low-priced agricultural and fishery byproducts, as well as improve meat production. Optimum inclusion amounts of defatted Haematococcus in tilapia diets should be tested for higher growth output and increased quality of meat products.