Effect of the use of the microalga Spirulina maxima as fish meal replacement in diets for tilapia, Oreochromis mossambicus (Peters), fry

The present study addresses the use of the microalga Spirulina maxima as a protein source in diets for tilapia, Oreochromis mossambicus (Peters), fry. Animal protein was replaced with algae protein at ratios of 20%, 40%, 60%, 80% and 100%, and the substitution effect was compared with a control diet in which fish meal was the sole protein, An additional 100% spirulina prot ein diet was supplemented with phosphorous to test for possible mineral def iciency in the plant-protein-based diet, The six treatments were tested in triplicate in a closed-recirculating system where the fish were fed by hand at 6% of their body weight, After a 9-week feeding period, the growth rate and protein utilization of fish fed the diet with 20% and 40% Spirulina we re elevated and not significantly different (P>0.05) from those fed the con trol diet, Further increases in the alga protein content significantly decr eased the growth and feeding performance, The addition of P to the 100% Spi rulina diet slightly improved performance in comparison to the same diet wi thout P, None of the treatments produced any clear adverse effects on carca ss composition, It is observed that Spirulina can replace up to 40% of the fish meal protein in tilapia diets.