Evaluation of a practical diet for juvenile tench (Tinca tinca L.) and substitution possibilities of fish meal by feather meal

A basal diet for juvenile tench (Tinca tinca) was formulated and used to test possibilities of replacement of fish meal (FM) by feather meal (FeM). A 120-day experiment was conducted with 5 month-old juveniles (27.45 mm total length, 0.308 g body weight). Three diets (500 g crude protein/kg) differing in the level of replacement of FM protein by FeM protein were prepared: 0 (basal diet), 0.25 (148 g FeM/kg) or 0.35 (210 g FeM/kg). Survival ranged from 0.96 to 0.97 (P=0.061). The basal diet enabled higher growth (59.3 mm total length, 2.6 g body weight, 1.74%/d specific growth rate; P<0.001) and lower feed conversion ratio (1.36; P=0.032) than the FeM diets. There were not significant differences in body weight and specific growth rate between 0.25 or 0.35 replacement of FM protein by FeM protein. The basal diet enabled satisfactory performance and low proportion of deformed fish (0.03), showing to be feasible for future studies on juvenile tench. The FeM inclusion at the levels tested reduced growth and increased the proportion of deformed fish.