NL193:Evaluation of optimum dietary protein-to-energy ratio in juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

Evaluation of optimum dietary protein-to-energy ratio in juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

Kang-Woong Kim, Xiaojie Wang, Se-Min Choi, Gun-Jun Park, Sungchul C. Bai-2004

Aquaculture Research, 35(3): 250-255

Abstract:

An 8-week feeding trial was conducted to estimate the optimum dietary protein to energy (P/E) ratio in juvenile olive flounder Paralichthys olivaceus. Eight experimental diets were formulated with two energy levels and four protein levels at each energy level. Two energy levels of 12.5 and 16.7 kJ g^-1 diets were included at crude protein (CP) levels of 25%, 30%, 35% and 45% with 12.5 kJ g^-1, and CP levels of 35%, 45%, 50% and 60% with 16.7 kJ g^-1. After 1 week of the conditioning period, fish initially averaging 8.1±0.08 g (mean±SD) were randomly distributed into the aquarium as groups of 15 fish. Each diet was fed on a dry-matter basis to fish in three randomly selected aquariums at a rate of 3-5% of total wet body weight per day for 8 weeks.

After 8 weeks of the feeding trial, weight gain (WG), feed efficiency ratio and specific growth rate of fish fed 45% CP with 16.7 kJ g^-1 energy diet were significantly higher than those from the other dietary treatments (P<0.05). WG of fish fed 12.5 kJ g^-1 energy diets increased with the increase of dietary protein levels. However, WG of fish fed 16.7 kJ g^-1 energy diets increased with the increase of dietary protein levels up to 45% CP and then decreased when fish fed 50% and 60% CP diets. Both dietary protein and energy affected protein retention efficiency and energy retention efficiency. Haemoglobin (Hb) of fish fed 35% and 45% CP diets with 12.5 kJ g^-1 energy were significantly high and not different from Hb of fish fed 45% and 50% CP diets with 16.7 kJ g^-1 energy. Haematocrit of fish fed 45% CP diet with 16.7 kJ g^-1 energy was significantly higher than those from fish fed 25% and 30% CP diets with 12.5 kJ g^-1 energy (P< 0.05). Based on the results of this experiment, we concluded that the optimum dietary P/E ratio was 27.5 mg protein kJ^-1 with diet containing 45% CP and 16.7 kJ g^-1 energy in juvenile olive flounder.

(Department of Aquaculture/Feeds & Foods Nutrition Research Center, College of Fisheries Science, Pukyong National University, 599-1 Daeyeon-3-dong, Nam-gu, Busan 608-737, Korea. E-mail of S C Bai: scbai@mail.pknu.ac.kr)

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