Evaluation of Dried Distillers Grains with Solubles Fed to Yellow Perch as a Fish-Meal Protein Replacer

Experimental blends were formulated to investigate use of dried distillers grains with solubles (DDGS; 38% crude protein, 5% lipid) as a fish meal replacer in yellow perch Perca flavescens diets. Four fish-meal replacement levels (25, 50, 75 and 100%) using DDGS were blended for comparison with a fish meal control diet. Feeds were processed using a pilot-scale twin screw extruder, using a 1.9 cm diameter circular die, and then fed to yellow perch (~24g) in a 105-d feeding trial. Diets (~3.06 kcal/g) were formulated to a protein content of 36% and lipid content of 10.5%. All pelleted diets exhibited high durability (89.9% to 96.7%) and excellent water stability (> 30 min). Survival, feed conversion efficiency (FCE), total consumption, relative growth (tank weight _{time b} – tank weight _{time a}/ tank weight _{time a} x 100), fillet color, Fulton-type condition factor (K), hepatosomatic index (HSI), protein efficiency ratio (PER), and dress-out percentage were determined at the conclusion of the trial; growth was measured every 21 days. No mortalities were observed during the feeding trial, but significant differences were found in relative growth (F=58.3, df 4, 20, P<0.01) , FCE (F=84.6, df 4, 20, P<0.01), total consumption (F=6.0, df 4, 20, P<0.01), PER (F=83.1, df 4, 20, P<0.01), and K (F=35.0, df 4, 20, P<0.01) with increasing DDGS levels. Treatment fish fed ≤50% DDGS replacement achieved the best growth performance. Fish fed diets containing >75% DDGS replacement failed to reach 100% growth from initial weights. Relative growth of fish fed diets containing 25% DDGS replacement was slightly lower but did not significantly differ from fish fed the control diet; growth in all other treatments was significantly lower. PER and FCE were lowest for fish fed diets containing >75% DDGS. Dress-out percentage and HSI were not significantly different and showed no correlation with DDGS concentrations. Fillet color was not significantly different among treatments; however, yellowness increased with increasing DDGS. Further testing of DDGS in combination with supplements is necessary to facilitate increased use by yellow perch.