The present experiment aimed to investigate the effect of organic fertilization and artificial feed, beside the addition of some untraditional feedstuffs as well as Biogen® to artificial feed on reducing feeding costs in tilapia culture. Twelve earthen ponds with the same area were stocked by Nile tilapia and represented 6 treatments (2 replicates for each). In the first treatment (T1), ponds were fertilized by 25 kg/day poultry litter throughout the experimental period (6 months). The same organic fertilization was used in the second treatment (T2) for 3 months followed by artificial feed (25% crude protein) during the following period (3 months). For the third treatment (T3), organic fertilization was applied during the whole experimental period and the artificial feed (2% of fish biomass) was applied during the last three months only. For the other three treatments (T4, T5 and T6) organic fertilization was applied for 3 months followed by feeding on artificial feed (25%CP) beside blue green algae, Azolla or Biogen® at a rate of 10, 10 and 2 kg/ton, respectively. Results of the experiment could be summarized as follows: - Water temperature ranged from 26.55 to 27.81°C; Dissolved oxygen (DO) from 3.40 to 5.58 mg/liter and pH from 8.19 to 8.64 with insignificant differences among the different treatments in water temperature and pH values. T1 had the greatest drop in the overall mean of phytoplankton and zooplankton number (organism/l) compared to the other experimental treatments. - T1 showed the lowest body weight (BW), body length (BL), weight gain (WG) and specific growth rate (SGR) while T6 gained the highest BW, BL, WG and SGR and the differences among treatments for these parameters were significant. - The final total fish yield was the lowest for fish fed the natural food only (T1). Compared to T1, the other feeding regimes T2, T3, T4, T5 and T6 increased the total fish yield by 54.2, 57.4, 59.9, 67.8 and 87.0%, respectively. - The averages dressing percentage found to be 57.72, 57.75, 58.34, 60.40, 61.36 and 61.50%; fish protein content were 67.93, 67.77, 68.19, 70.66, 71.84 and 72.74 for T1, T2, T3, T4, T5 and T6, respectively and the differences among these percentages were significant (P |
