Origanum vulgar Levels  in experimental rations Items Control-0.0 0.50% 1% 1.50% Price/kg feed P.T 2.78 2.93 3.08 3.23 FCR (kg feed/kg gain) 2.01 1.67 1.72 1.86 Feed cost/kg gain P.T 5.59 4.89 5.3 6.01 Reduction cost in kg gain 100 12.52 5.19 -7.51

Table 6: Economic efficiency for production of one Kg gain of fingerlings Nile tilapia O. niloticus fed diets containing different levels of extracted Origanum vulgare.