PRODUCTION OF OMEGA-3 ENRICHED TILAPIA THROUGH THE USE OF A COMMERCIALLY AVAILABLE SEAWEED BLEND

Tilapia are a relatively low-fat fish and subsequently contain relatively low levels of healthy omega-3 fatty acids. Countless studies have shown that omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are integral for fetal neural development, can help prevent dementia and Alzheimer's, reduce the risk of heart disease, improve eyesight, and can serve as a general anti-inflammatory agent. Fish that are high in omega-3, such as salmon, enjoy the benefits of being promoted as a healthy fish for consumers. The primary aim of this study is to increase the concentrations of omega-3 fatty acids in farm- raised tilapia to create a value added product that will benefit both consumers and producers.

An 8-week feeding trial comparing nine diets including: control diet, commercial diet, three diets fortified with 1%, 3%, and 5% fish oil BW (Omega Protein) respectively, three diets fortified with 1.7%, 5.19%, and 8.65% kelp blend BW (Ocean Harvest) each with 3% fish oil, as well as an additional 5.19% kelp plus 1% fish oil diet. The trial was conducted using 450 juvenile tilapia, distributed evenly amongst 18, 265-L tanks. Recirculating aquaculture systems were outfitted with bioreactors, bubble bead filters, ultra violet sterilization and aeration. Temperature and dissolved oxygen were tested daily and ammonia, nitrite, nitrate, and pH were measured several times a 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. 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 health throughout the feeding trial. There were no significant differences in mean survival (range, 96-100%), weight gain (319-400 grams), food conversion ratio (1.24-1.50) across all treatments. There was also no significant difference in: fillet yield (42-45%, 44-46%) at 4 and 8 weeks, respectively, VSI (2.4-3.8), HSI (1.51-1.83), across all treatments. Fish fed the 1, 3 and 5% Kelp diets for 8 weeks were significantly (P<0.05) heavier than those fed the commercial diet (483-587 grams). No other significant differences in growth were observed. Other impacts of the diet will be presented at the conference.