Growth of juvenile Asian seabass, Lates calcarifer, fed varying carbohydrate and lipid levels

Abstract

Growth performance of juvenile seabass (initial mean body weight, 0.90 ± 0.04 g) fed varying carbohydrate and lipid levels were determined using practical diets in a 2 × 3 factorial experiment. Two carbohydrate levels (15 and 20%) and three lipid levels (6, 12 and 18%) at a fixed protein level of 42.5% were tested. Dietary energy ranged from 284 to 412kcal 100g⁻¹ diet. The fish were reared for 12 weeks in 601 flow-through tanks with aeration in seawater at 32%. and at 26.5–29 °C.

Higher weight gains were observed in fish fed diets containing 20% carbohydrate with 12 or 18% lipid. Lowest specific growth rate was observed in fish fed the 15% carbohydrate at 6% lipid. Survival was 100% in all treatments. The feed conversion ratios for fish fed 20% carbohydrate at 12 or 18% lipid, and 15% carbohydrate with 12% lipid were best. Specific growth rate and weight gain did not differ at lower dietary lipid (12-6% or 18-12%) despite an increase of dietary carbohydrate indicating a sparing of lipid by carbohydrate as an energy source. Dietary lipid at 18% (1:1 ratio of cod liver oil and soybean oil) seems to be excessive for seabass. Based on this study, we recommend a carbohydrate level of 20% in diets containing lipid levels ranging from 6 to 18%.