NUTRIENT COMPOSITION OF LOCAL INGREDIENTS & THEIR DIET ON GROWTH OF TILAPIA IN FRESHWATER & SALTWATER

There are many tropical agricultural and fishery byproducts available in Hawaii, as well as other US Pacific Islands, yet no commercial aquatic feeds are produced in these areas. Aquaculture production still relies solely on imported feeds from the mainland. Expensive feed costs limit local aquaculture development. It is necessary to analyze nutrient compositions of locally available ingredients and develop local-made feed for the local aquaculture industry.  

Over ten ingredients were collected from Hawaii and the Pacific Islands and their proximate and mineral contents, gross energy values, and amino acid and fatty acid profiles were analyzed. The local fishmeal was measured with 58.9% crude protein, 8.64% crude lipid, 21.41% ash and 4344 Cal/g of gross energy value. The fishmeal was rich in contents of essential nutrients, including amino acids, lysine (7.88%) and methionine (4.47%), and fatty acid, docosahexaenoic acid (11.4%). Local microalgae byproducts, spirulina and defatted Haematococcus, contained high crude protein (53.7% and 40.3%, respectively) and could be used as protein ingredients in aquatic feed. Local cassava and copra meal had high carbohydrate contents (96.7% and 60.2%) and could be used as energy ingredients. A diet was formulated and processed using these local ingredients, and an 8-week feeding trial was conducted on juvenile tilapia (Oreochromis mossambicus) in freshwater and saltwater. Results showed that specific growth rates of tilapia were 3.62 % /day in freshwater and 3.71 % /day in saltwater for the local-made diet; commercial feed achieved better growth rates probably because it contained higher protein (44.0%) than the tested diet (39.1%).

The results of this study indicated that local products or byproducts could be used as feed ingredients for aquatic feed production. The tested ingredients have high available amounts and reasonably low prices; their aquaculture application will benefit the local economy and protect the environment.