Growth of juveniles of the fat snook, Centropomus parallelus, in response to dietary lipid, energy and protein

Abstract

This study evaluated the growth of fat snook Centropomus parallelus in response to the dietary total lipids, gross energy (GE) and crude protein (CP) content. In the 1st experiment, five isonitrogenous diets with 541.7 ± 2.4 g kg-1 CP varied their lipid content in 113, 151, 160, 189 and 200 g kg-1 and GE in 18.8, 19.4, 20.4, 21.2 and 22.2 MJ kg-1, respectively. A total of 300 fish with 6.5 ± 2.4 g were stocked in 30 tanks of 1 m3 under 10 fish m- ³ and reared for 96 days. There were no differences in fish final body weight (38.2 ± 12.5 g), daily weight gain (DWG, 0.35 ± 0.04 g day-1) and specific growth rate (SGR, 1.92 ± 0.11 day-1) among dietary treatments. Feed conversion ratio (FCR) was 1.76 ± 0.17 with a protein efficiency ratio of 1.06 ± 0.10. The viscerosomatic (VSI) and visceral fat indices (VFI) raised significantly with an increase in the dietary lipid while the hepatosomatic index (HSI) was unaffected. There was a significant reduction in feed intake as the dietary lipid content reached 189 g kg-1. In a 2nd study, five isolipidic diets (114.4 ± 1.9 g kg-1 lipids) with decreasing levels of CP and GE of 578, 535, 505, 465, and 430 g kg-1 and 20.5, 19.9, 19.4, 18.9, and 18.1 MJ kg-1, respectively, were evaluated. A total of 1,450 fish of 5.8 ± 2.1 g were reared in 30 tanks of 5.8 m³ under 10 fish m-3 for 93 days. Final survival reached 93.5 ± 5.5%. Fish DWG (0.27 ± 0.05 g day-1) and SGR (1.78 ± 0.11 % day-1) did not vary in response to dietary CP. Final body weight significantly reduced while HSI increased in fish fed the 430 g kg-1 CP diet compared with fish fed the 578 g kg-1 CP diet. Results of this work indicated that fish between 5.8 g and 40.8 g wet body weight can maximize growth when fed diets containing 113.2 g kg-1 lipids, 540.5 g kg-1 CP and a 34.7 MJ kg-1 energy to protein ratio.