Dietary lipid requirement of juvenile white-leg shrimp, Penaeus vannamei (Boone, 1931) reared in inland ground saline water of 15 ppt

A 60-day feeding trial was conducted to evaluate the optimum dietary lipid level in terms of growth performance, digestive enzymes and hemato-biochemical parameters of white-leg shrimp, Penaeus vannamei juveniles in inland ground saline water (IGSW) of 15 ppt salinity. The shrimps (avg. wt., 4.04 +/- 0.03 g) were randomly distributed in six groups in triplicates (15 shrimps/tank, 290 L), viz., TCL40 (40 g/kg lipid)(,) TCL60 (60 g/kg lipid)(,) TCL80 (80 g/kg lipid), TCL100 (100 g/kg lipid), TCL120 (120 g/kg lipid) and TCL140 (140 g/kg lipid). Six semi-purified hetero-lipidic (40-140 g lipid/kg), hetero-caloric (376-426 Kcal DE/100 g) and iso-nitrogenous (400 g crude protein/kg) diets were prepared and fed to respective groups four times daily. Weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) showed higher quadratic relations (R-2 = 0.97, 0.98, 0.94 and 0.87, respectively) to dietary lipid levels (p < 0.05) with enhancing dietary lipid up to 60 g/kg. Whole body moisture and lipid contents exhibited a high linear (R-2 = 0.87 and 0.98) and quadratic (R-2 = 0.88 and 0.98) (p < 0.05) inverse relationship with enhancing dietary lipid levels up to 140 g/kg. Hemolymph hemocyanin, serum total protein and glucose level did not differ significantly (p > 0.05), but the TCL60 group showed significantly (p < 0.05) higher serum cholesterol and triglyceride levels. Serum osmolality, osmoregulatory capacity, and branchial Na+/K+-ATPase activity was similar (p > 0.05) among the groups. Hepatopancreatic lipase and amylase activity significantly (p < 0.05) increased, but trypsin activity did not vary significantly (p > 0.05) among the groups. Second-degree polynomial analysis with WG, SGR and FCR indicated that a 55.80-58.80 g lipid/kg diet is optimum for P. vannamei juveniles in IGSW of 15 ppt salinity.