Effect of dietary lipid level on nutritional performance of the surubim, Pseudoplatystoma coruscans

摘要

Four diets were formulated to contain a constant protein level (46%) and four different lipid levels (6%, 10%, 14% and 18%). The diets were fed to surubim, a Brazilian native carnivorous freshwater fish. Gross energy of the diets were 4440, 4650, 4840, and 5140 (kcal/kg). Surubim fingerlings (average weight: 2.72 g/fish) were randomly assigned to treatments and fed the test diets twice a day to apparent satiation for 62 days. The study was conducted in triplicate with 13 fish distributed in 60-1 net-cages set up in 1000-1 plastic tanks (three cages per tank), equipped with a flow through freshwater system and water temperature of 27+/-1 degreesC. The diet with 6% lipid gave the poorest performance, while fish fed the highest lipid level showed the best nutritional performance. Feed conversion ratio and daily feed consumption showed a marked decrease (P<0.05) in inverse proportion to lipid level in the diet. Proximate composition of fish whole body was markedly affected (P<0.05) by dietary lipid, particularly in relation to moisture and crude lipid. Visceral lipid content and nutrient retention also increased in direct proportion to the dietary lipid level (P<0.05). Results of the present study indicate that soybean lipid is well metabolized by this species, serving as a source of energy and promoting excellent growth.