has the lowest FCR and the second highest weight gain (which was
not different from the highest).
Because fish can meet a substantial part of their energy
requirement from dietary protein, the protein to energy (P/E) ratio
is extremely influential on feed conversion efficiency, especially the
efficiency of protein and energy utilization (Webster et al., 1995; Reis
et al., 1989). Improper dietary protein, energy levels and/or their ratio
will lead to an increase in fish production cost and the deterioration of
water quality resulting from wasted feed (Lee et al., 2000). The
interval of P/E ratios among all treatments in this study is somewhat
narrow, but this little difference significantly affected growth and feed
utilization of blunt snout bream. The maximum weight gain was
obtained in fish fed a diet containing a P/E ratio of 19.28 g protein/MJ.
However, the best FCR was observed in fish fed the diet with a P/E
ratio of 17.14 g protein/MJ. A positive correlation was found between
dietary P/E ratios and weight gain of fish fed diets with 7% and 10%
lipid. However, lower P/E ratios yielded better growth at the same
protein level (at 4% and 7% lipid). This indicates that adequate levels of
protein and energy in diets must be carefully considered when
optimum P/E ratio is estimated as has been described by Garling and
Wilson (1976).
Survival rates were high (97–100%) in the present study except for
that of fish fed diet 7 (35% protein: 4% lipid) (92.33%). This was perhaps
due to the fact that diet 7 contained the highest P/E ratio (19.45 g