PRODUCTION OF OMEGA-3 ENRICHED TILAPIA THROUGH THE USE OF A COMMERCIALLY AVAILABLE Schizochytrium sp. ADDITIVE

Worldwide production of tilapia has increased by more than 300% since 2003, with global supply and demand expected to continue to grow in the coming decades. Tilapia are relatively lean fish with low levels of omega-3 fats. Consuming foods rich in omega-3 fats such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can improve human health and function in the areas of the brain, heart and circulatory systems, joints, and eyesight. The primary aim of this study was to investigate if we can increase the omega-3 levels and improve the omega 3:6 ratio in farm-raised tilapia. Such an enhanced tilapia fillet will benefit consumers and will increase the value of tilapia for aquaculture producers.

An 8-week feeding trial was conducted comparing eight diets including: a control diet, commercial diet, 1%, 3%, and 5% fish oil BW (Omega Protein) diets, and 1.75%, 5.26%, and 8.77% Schizochytrium sp. meal (Alltech ALL-G-Rich) diets. The ALL-G-Rich diets were formulated to be iso-omega-3 to the fish oil diets. The feeding trial was conducted using 400 juvenile tilapia, distributed evenly amongst 16, 265-L tanks. Recirculating aquaculture systems, including bioreactors, bubble bead filters, ultra violet sterilization and aeration were used to maintain ideal conditions for tilapia culture. Temperature and dissolved oxygen were tested daily and ammonia, nitrite, nitrate, and pH were measured several times each week. A typical omega-3 deficient corn oil based diet was used as a control. Fish were weighed on a weekly basis to adjust feed rations, track growth rates and feed conversion ratios. Eight fish from each treatment were sampled at weeks 4 and 8 in order to determine muscle ratios (fillet yields). These eight fish were then pooled into 4 samples per treatment and tissue samples of fillet and rib meat were collected at weeks 4 and 8. Liver and mesenteric fat tissue samples were also collected at week 8. The lipid in all tissue samples was extracted and approximately 30 mg was methylated. Fatty acid methyl esters were then identified and quantified using a Shimadzu GCMS-QP2010. Statistical analysis was performed using JMP.

Fish demonstrated positive growth and good health throughout the feeding trial. There were no significant differences among fish fed the various diets for mean survival (range, 96-100%), weight gain (319-403 grams), and food conversion ratio (1.24-1.50). There also was no significant difference in: fillet yield (42 -45%, 44-46%) at 4 and 8 weeks, respectively, VSI (2.45-3.05), HSI (1.51-1.83), across all treatments. Fish fed the 1% algae diet for 8 weeks were significantly (P<0.05) heavier than those fed the 5% algae or commercial diets (581 to 495 and 483 grams, respectively). Other impacts of the diet on fish production and health will be presented at the conference.