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pp.12-18
A field study was conducted to compare growth, feed utilization and nutrient excretions by feeding extruded pellet (EP) and moist pellet (MP). Slow growing flounder were used as the experimental animal to find out a prominent result in terms of growth and feed utilization. Weight gain of fish fed the experimental diets for 8 weeks reached 105.3 g for EP and 107.1 g for MP, while fresh feed intake was 98.7 g for EP and 279.4 g for MP. Feed conversion ratio was 0.94 and 2.61 for EP and MP, respectively which was 0.77 and 0.94 when corrected on dry matter basis. Even though protein efficiency ratio (2.26 vs 2.21), specific growth rate (0.69% vs 0.70%), daily weight gain (2.06 g vs 2.10 g) and mortality (4.0% vs 4.1%) were similar between EP and MP, protein retention efficiency of fish fed EP was superior (53.3%) to that of fish fed MP (39.6%). Protein intake of fish for 8 weeks was similar from 52.3 g for EP to 53.3 g for MP, while protein gain was higher in fish fed EP (27.9 g) than in fish fed MP (21.1 g). Protein excretion by feeding EP and MP reached 232 g and 300 g, respectively per kg gain, suggesting that protein loads could be greatly reduced in practical culture system through the use of EP. Phosphorus (P) intake was much lower in fish fed EP (1.63 g) than in fish fed MP (2.18 g), while retention of P was higher in fish fed EP (0.88 g) than in fish fed MP (0.78 g), showing the retention efficiency of 54.0% and 35.9%, respectively. Fish fed EP excreted 7.1 g of P per kg gain which was much lower than that of fish fed MP (13.1 g). The present results clearly showed that EP feeding for flounder is not only productive but also environmentally friendly.
