Brewer’s yeast as a protein source in the diet of tilapia (Oreochromis niloticus) and freshwater prawns (Macrobrachium rosenbergii) reared in a clear water or biofloc environment

This thesis investigated the effects of dietary protein replacement of fishmeal or soybean meal with spent brewer’s yeast (SBY) in farmed tilapia and giant freshwater prawns. The effect of rearing tilapia and prawn in two different rearing systems, clear water recirculating aquaculture system (CW-RAS) and biofloc recirculating aquaculture system (Bio-RAS), were also investigated. The fish reared in Bio-RAS displayed higher growth, a higher protein efficiency ratio and a lower feed conversion rate than fish reared in CW-RAS. This difference between systems was not as apparent in the growth and protein efficiency ratio of freshwater prawns. In freshwater prawns, the survival rate was not affected by aquaculture water system nor by the replacement of fishmeal with SBY. The growth performance of prawns was not significantly different between any dietary treatments in Bio-RAS or CW-RAS. Significant differences were only found between brewer’s yeast replaced fishmeal at 60% in a CW-RAS and at 40% in Bio-RAS. Tilapia reared in CW-RAS with replacement of fishmeal with SBY showed a significantly (p