Yellow Perch Perca flavescens Nutrient Utilization and Performance Fed Grower Diet Formulations with Soy Protein Concentrate

Soy protein concentrate (SPC; 54% crude protein, 1% lipid) was used as a protein replacer for fish meal (FM) protein in experimental feeds formulated for yellow perch Perca flavescens. Four fish-meal replacement levels (25, 50, 75, and 100%) using SPC were compared with a fish meal control diet. Experimental feeds were processed using a pilot-scale Wenger twin screw extruder, using a 1.9 cm diameter circular die, and then fed to juvenile yellow perch (~26g). All pelleted diets exhibited high durability (96.7% to 98.8%) and excellent water stability (> 30 min). Survival, feed conversion efficiency (FCE), feed consumption, and dress-out percentage were determined after a 105-d feeding trial; growth was measured every 21 days. No mortalities were observed during the feeding trial.  Growth rates were significantly different among all treatments (F = 31.3, df 4, 19, P < 0.01) and negatively correlated with increasing SPC levels (r = -0.93, P < 0.01).  Feed efficiency was also significantly different (F = 16.4, df 4, 19, P < 0.01) and negatively correlated with increasing SPC levels (r = -0.88, P < 0.01). Consumption was not significantly different among experimental diets (F=2.76, df 4, 19, P=0.06), although it was negatively correlated with increasing SPC levels (r = -0.61, P = 0.06).  Dress-out percentage was significantly different (F = 3.01, df 4, 19, P = 0.04), however no relationship was found with SPC concentration. Based on growth rates and feed efficiency, diets containing >25% SPC without supplements does not provide performance comparable to a fish-meal based diet.