Growth variability of brown trout fry (Salmo trutta morpha fario Linnaeus, 1758) affected by differentiated diet during initial rearing

The aim of this study was to assess the effect of differentiated nutrition on the sac-fry growth intensity of brown trout (Salmo trutta m. fario). In this experiment two dry feed mixtures with different feeding program were used. Sac-fry rearing was realized in throughs with volume of 700 L during 113 days. During the rearing period was the feed mixture feed ad libitum. First tested group of fish (group A) was fed by mixture with different nutrient composition (crude proteins 56 % and 50 %, fat 12 % and 20 %) for individual rearing stages. Second tested group of fish (group B) was fed by mixtures with constant nutrient composition (crude proteins 57 %, fat 15 %) for all rearing period. It was found that the group A had better results for estimated growth parameters (Lt=48.37 ±2.41 mm; w=1.32 ±0.30 g; CF=0.84; SLGR=0.63 %.d-1; SWGR=2.12 -1) in comparison to group B (Lt=42.90 ±2.23 mm; w=1.20 ±0.32 g; CF=0.83; SLGR=0.52 %.d-1; SWGR=2.04 %.d-1). Attained results confirm that the application of mixture with different nutrient composition has a positive effect on the growth parameters on brown trout sac-fry rearing