Growth, nitrogen and energy utilization of juveniles from four salmonid species: diet, species and size effects

The effect of dietary digestible protein/digestible energy (DP/DE) ratio on growth, feed efficiency (FE), digestibility, nitrogen (N) and energy utilization, and body composition of juveniles from four salmonid species reared in freshwater was investigated in a series of trials. Another objective of this study was to investigate how the FE, and N and energy utilization changed as fish grew. Four diets were formulated to be isoenergetic (DE=20 MJ/kg) but contain different DP/DE ratios, 24, 22, 20, and 18 g/MJ, achieved through reduction of DP level (53% to 39%) and increase of lipid level (19% to 26%). Diets were hand-fed to near-satiety to triplicate groups of lake trout (initial body weight (IBW), 47 g) and Atlantic salmon (IBW, 25 g) for 280 days at 13 °C and to rainbow trout (IBW, 47 g) and chinook salmon (IBW, 24 g) for 84 and 140 days, respectively, at 12 °C. Within species, weight gain was not affected by DP/DE (P