EVALUATING SPIRULINA AS AN ALTERNATIVE PROTEIN SOURCE IN NILE TILAPIA Oreochromis niloticus GROW-OUT DIETS  

The amount of feed required to sustain aquaculture growth is increasing. This will put a strain on aquafeed ingredient resources. A shift away from relying on ecologically and economically problematic fishmeal and towards terrestrial plant products has already taken place. Plant proteins are, however, nutritionally incomplete, and are used by many other competing industries (e.g. biofuels, and human consumption). As such, other nutritionally appropriate, and non-competitive protein sources should be explored. The FAO has recommended investigating Spirulina as an aquafeed ingredient. Spirulina is nutritionally appropriate, and relatively digestible, but has questionable effectiveness as a primary protein source in grow-out diets.

This study will evaluate the use of Spirulina as an alternative protein source in tilapia grow-out diets. Four experimental diets were formulated to contain 0, 15, 30, and 45% dry matter Spirulina (SBM, SP1, SP2, SP3 respectively) (Table 1). One commercially available tilapia diet was included for reference (CC). Four replicate aquaria were assigned to each of the diets and we monitored feed intake, growth, and ammonia and phosphorus production for four weeks.  A separate digestibility (the Guelph method) and palatability trial will also take place, and the use of feed enhancers to improve experimental feed intake will be evaluated.

We will present results for feed palatability, digestibility, waste output, carcass composition, and fish growth. We will also present a cost-benefit analysis of each feed and comment on which feed is appropriate for small-scale RAS producers.  

Preliminary results suggest that SP1 and CC are the most palatable, and most effective growth promoting feeds.