Lysine Supplementation of the Protein Concentrate of Crinkle Grass Rhizoclonium riparium var implexum as an Ingredient in the Diet of Nile Tilapia Fry

A study was conducted on 1000 fish, to evaluate the effect of supplementing crystalline lysine (Lys) to a diet containing protein concentrate from seaweed Rhizoclonium riparium var implexum (RPC) on the performance of Nile tilapia fry. A previous finding showed that protein concentrate was deficient in lysine. Four experimental diets were prepared: Diet 1 - no RPC and no Lys; Diet 2 - 8.4% RPC+0.5% Lys; Diet 3 - 8.4% RPC+1.0% Lys; and Diet 4 - 12.6% RPC+1.5% Lys. After a 60 day feeding trial, results showed that final average body weight, weight gain, protein accumulation, and whole body biochemical composition were not affected by the dietary treatment. Specific growth rate, food conversion ratio, and protein efficiency ratio were all significantly higher in fish fed the test diets (i.e. Diets 2, 3 and 4) than in those fed the control diet. There were no significant differences in protein and energy retention; lipid retention was lowest in Diet 2 group and statistically similar to Diet 3 and 4 groups. In conclusion, most parameters improved significantly in fish fed diets with RPC and Lys supplementation compared to fish in the control group. The most cost effective dietary treatment was Diet 2 containing 8.4% Rhizoclonium protein concentrate supplemented with 0.5% crystalline lysine.