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The optimal mixed feeding schedule for mono-sex male Nile tilapia (Oreochromis niloticus) was investigated in the current study. The fish (4.01 ± 0.02 g initial weight and 5.84 ± 0.04 cm initial length) were fed up to satiation with high protein (HP, 32.80 % protein on dry basis) and low protein (LP, 28.64 % protein on dry basis) diets in different schedules: alternately every other day (1HP/1 L P), alternately every other week (7HP/7 L P) and alternately every two weeks (14HP/14 L P), in comparison to continuously feeding by HP (positive control) or by LP (negative control) alone. At the end of eight weeks of trial, superior growth performance and feed utilization were observed in fish receiving HP, 1HP/1 L P and 7HP/7 L P relative to the remaining treatments. The specific activity of digestive enzymes (pepsin, trypsin, amylase, lipase, and activity ratio of amylase to trypsin) was modulated, indicating physiological responses for improving nutrient utilization due to the different feeding regimens. All fish mainly utilized carbohydrates rather than lipid and protein, or probably the protein-sparing effect was predominant, as indicated by the positive correlation between amylase specific activity and protein efficiency ratio (r = 0.681, P < 0.01), across five feeding schedules. There were no negative effects of mixed feeding schedules on flesh quality and carcass composition in any experimental group. However, based on economic analysis, fish receiving 1HP/1LP schedule had reduced cost of tilapia production relative to the other treatments. Therefore, the optimal feeding schedule for mono-sex male tilapia is 1HP/1LP, which should be used as a practical feeding guideline for mono-sex male Nile tilapia production.
Rodjaroen et al. (Tue,) studied this question.