The present study was designed to evaluate the effect of replacing the protein source of soybean meal (SBM) by tomato by-product meal (TBM) and replacing yellow corn (YC) by potato by-product meal (PBM) on growth performance and feed utilization of Nile tilapia, O. niloticus. Therefore, two experiments were conducted, in the first experiment nine experimental diets were formulated to contains 0 to 80% replacing levels of SBM by TBM in 10% increments. In the second experiment another nine experimental diets were formulated to contains 0 to 80% replacing levels of YC by PBM in 10% increments and each diet was fed to two replicates. Experimental diets of the two experiments were formulated to be isonitrogenous (30% CP) and isocaloric (3300 ME/kg diet) and P/E ratio of 90 mg protein/kcal (ME). During the two experimental periods diets were fed to Nile tilapia (O. niloticus) 6 days/week at 4% of live body weight through 10 weeks experimental period. Results of the first experiment showed that:
Replacement of SBM by TBM up to 50% did not affect fish body weight (BW), body length (BL) weight gain (WG), specific growth rate (SGR), feed intake (FI), feed conversion ratio (FCR) and protein efficiency ratio (PER). Also, replacing 50% of SBM by TBM did not exert significant effect on the dress-out, by-products, flesh, moisture and protein content in fish bodies.
Results of the second experiment showed that replacing YC in tilapia diets by PBM up to 40% did not significantly affect all growth parameters (BW, BL, WG and SGR), feed utilization (FI, FCR and PER) and the same trend was also observed for flesh, moisture, protein, fat and ash contents in fish bodies.
From economic view, it was observed that replacing 50% of SBM by TBM in tilapia diets reduces feed costs by 10.93% while replacing 40% of YC by PBM reduced feed costs by 7.53%.
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