Growth and body composition of juvenile white shrimp, Litopenaeus vannamei, fed different ratios of dietary protein to energy

A 10-week feeding experiment was conducted to evaluate the effect of different protein to energy ratios on growth and body composition of juvenile Litopenaeus vannamei (initial average weight of 0.09 +/- 0.002 g, mean +/- SE). Twelve practical test diets were formulated to contain four protein levels (300, 340, 380 and 420 g kg(-1)) and three lipid levels (50, 75 and 100 g kg(-1)). Each diet was randomly fed to triplicate groups of 30 shrimps per tank (260 L). The water temperature was 28.5 +/- 2 degrees C and the salinity was 28 +/- 1 g L-1 during the experimental period. The results showed that the growth was significantly (P < 0.05) affected by dietary treatments. Shrimps fed the diets containing 300 g kg(-1) protein showed the poorest growth. However, shrimp fed the 75 g kg(-1) lipid diets had only slightly higher growth than that fed 50 g kg(-1) lipid diets at the same dietary protein level, and even a little decline in growth with the further increase of dietary lipid to 100 g kg(-1). Shrimp fed the diet with 420 g kg(-1)protein and 75 g kg(-1) lipid had the highest specific growth rate. However, shrimp fed the diet with 340 g kg(-1) protein and 75 g kg(-1) lipid showed comparable growth, and had the highest protein efficiency ratio, energy retention and feed efficiency ratio among dietary treatments. Triglycerides and total cholesterol in the serum of shrimp increased with increasing dietary lipid level at the same dietary protein level. Body lipid and energy increased with increasing dietary lipid level irrespective of dietary protein. Results of the present study showed that the diet containing 340 g kg(-1) protein and 75 g kg(-1) lipid with digestible protein/digestible energy of 21.1 mg kJ(-1) is optimum for L. vannamei, and the increase of dietary lipid level has not efficient protein-sparing effect.