Optimum dietary lipid requirement of Pangasianodon hypophthalmus juveniles in relation to growth,fatty acid profile,body indices and digestive enzyme activity

Abstract

The present experimental trial was conducted to determine the optimal dietary lipid requirement of juveniles of Pangasianodon hypophthalmus (Sauvage, 1878) commonly referred to as the striped catfish using completely randomized design (CRD). Purified diets with five different dietary lipid levels 3, 6, 9, 12 and 15%; fish oil/sunflower oil (1:1) were used to feed triplicate groups of Pangasius with initial mean weight of 13.54–14.12 g twice a dayfor 8weeks.The highest weight gain(P <0.05) was observedin fishfed with9and12% lipid diets, followed by diet with6% lipid, thenby 15% lipid diet, and thelowest weight gain was observed in fish fed with 3% lipid. Other parameters such as specific growth rate (SGR), feedefficiency(FE)andprotein efficiency ratio(PER) showedthesametrendofweight gain. The hepatosomatic index (HSI), viscerosomatic index (VSI) and intraperitoneal fat (IPF) values increased with the increase of dietary lipid level. The feed conversion ratio (FCR) (P < 0.05) showed significant effects (P < 0.05) with variations in dietary lipid levels. The minimum FCR(1.95) was observed at 9%lipid inclusion-fed fishes and maximum FCR (3.53) was noticed at 3% lipid inclusion fed fishes .Higher and lower digestive enzyme activities were respectively observed in 9 and 15% lipid diets. The muscle fatty acid profile also varied with different dietary lipid levels. The higher level ofω-3,ω-6 fatty acid contents was recorded in the muscle of fish fed with 9% lipid diet,and lower level of fatty acid content was recorded in fish fed with 3% lipid diet. However, using second-order polynomial regression analysis, the optimal dietary lipid requirement of P. hypophthalmus juveniles was found to be 10.1%.