Lipid nutrition of juvenile Litopenaeus vannamei: I. Dietary cholesterol and de-oiled soy lecithin requirements and their interaction

Two 6-week experiments were conducted in recirculating systems to determine dietary requirements of Litopenaeus vannamei for phospholipids (PL) and cholesterol, and their potential interaction. A 3×4 factorial design consisting of three cholesterol levels (0%, 0.2%, and 0.5% of diet) and four PL levels (0%, 1.5%, 3.0%, and 5.0% of diet) provided by de-oiled soybean lecithin (SL) was applied. Overall survival was 97.7% with no significant difference among dietary treatments. There was a highly significant interaction between PL and cholesterol on shrimp growth (P=0.0001). Dietary cholesterol at 0.2% or 0.5% gave similar shrimp growth at any given level of PL.

In a second factorial experiment, the same four levels of PL were evaluated in conjunction with smaller intervals between dietary cholesterol levels, 0%, 0.05%, 0.1%, 0.2%, and 0.4%, in an attempt to define dietary requirements and interaction better. Overall survival was 99.7%. A highly significant interaction between dietary PL and cholesterol on growth of shrimp was detected again (P=0.0001). The cholesterol requirement was estimated to be 0.35% of diet in the absence of supplemental PL. At 1.5% and 3% PL, dietary cholesterol requirements were reduced to 0.14% and 0.13% of diet, respectively. When PL were provided at 5% of diet, 0.05% dietary cholesterol was needed for optimal growth. Shrimp growth was significantly enhanced as level of PL increased, but as the level of dietary cholesterol level increased, the growth-promoting effect of PL was diminished. Lipid composition of hepatopancreas (mid-gut gland) and muscle tissue of shrimp fed the different diets was also analyzed. Diets supplemented with PL resulted in higher total lipid in hepatopancreas and lower total lipid in muscle of shrimp than those of shrimp fed diets without supplemental PL. Interaction between dietary PL and cholesterol also affected total lipid and triglycerides (TG) in the hepatopancreas, as well as cholesterol concentration in the muscle.