Effects of graded dietary lipid levels on growth, feed utilization, body composition and metabolism in juvenile white leg shrimp, Penaeus vannamei (Boone, 1931) reared in inland saline water of 10 g/L salinity

A feeding trial was performed for 60 days to determine the dietary lipid requirement of Penaeus vannamei juveniles reared in inland saline water (ISW) of 10 g/L salinity. Six iso-nitrogenous (360 g/kg crude protein) and heterocaloric (15.4-17.6 KJ DE/g) semi-purified diets were prepared with graded level of lipid viz., 20, 40, 60, 80, 100 and 120 g/kg (L2-L12 with 20 g/kg incremental level). Two hundred and seventy P. vannamei juveniles (5.51 +/- 0.01 g) were randomly allocated (15 shrimps/200 L) into six treatment groups in triplicate following a completely randomized design. The shrimp of L4 and L6 groups exhibited significantly higher per cent weight gain (WG%), specific growth rate and protein efficiency ratio and the lowest feed conversion ratio. The lipid efficiency ratio and hepatopancreatic somatic index were significantly decreased and increased with increasing levels of lipid respectively. The L6, L8 and L10 groups exhibited significantly higher (p < .05) lipase activity. Shrimp of higher dietary lipid fed groups exhibited significantly higher (p < .05) aminotransferase activity than their lower dietary lipid fed counterparts. Based on WG% data, broken-line linear and second-order polynomial regression analysis showed that the optimal dietary lipid requirement of P. vannamei in ISW of 10 g/L salinity was 46.5 and 51.4 g/kg respectively.