Optimal lipid:carbohydrate and protein:energy ratios in semi-purified diets for juvenile black tiger shrimp <i>Penaeus monodon</i> Fabricius

Abstract

This study aimed at determining the optimal lipid:carbohydrate and protein:energy ratios for growth and survival of juvenile Penaeus monodon Fabricius. Two experiments were performed using completely randomized designs in semi-closed recirculating water systems. Juveniles of 0.4–0.8 g in weight and 4.0–5.5 cm in length stocked at a density of 80 individuals m− 2 were fed semi-purified diets. The first experiment determined optimal lipid:carbohydrate using isonitrogenous (35%) and isocaloric (330 kcal 100 g− 1) diets with five lipid:carbohydrate ratios: 4:39, 7:32, 9:25, 14:18 and 16:12 (% wt/wt). The lipid:carbohydrate ratio of 7:32 gave the highest growth rate (P < 0.05), while survival rates of shrimp in all other diet groups were similar but less. Thus, optimal lipid:carbohydrate ratio for the juvenile tiger shrimp was ≈ 1:4.6. In the second experiment, optimal protein:energy (P:E) ratio was studied using five protein levels (25%, 30%, 35%, 40% and 45%) with a fixed lipid:carbohydrate ratio of 1:4.6. Nine diets containing energy content (203–459 kcal 100 g− 1) with protein:energy ratio (63–171 mg protein kcal− 1) were formulated. Shrimp fed the diet containing 33–44% protein and an energy content of 223–371 kcal 100 g− 1 had a significantly higher growth rate than those fed the other diets (P < 0.05). A regression analysis indicated that an optimal P:E ratio for optimal growth and survival of juvenile tiger shrimp was 150 and 146 mg protein kcal− 1 respectively. This diet contained 33–44% protein and had optimal energy of 263–331 kcal 100 g− 1.