Evaluation of Plant-Based Proteins as Fish meal Replacements in Yellow Perch Diets

Feeds are crucial elements in aquaculture and can represent up to 70% of total operation costs. Generally the most expensive ingredient in fish feed is protein with fish meal (FM) being the primary protein source used in fish feeds. As a result to declining supplies and rising costs alternative protein sources are being tested as replacements for fish meal. Dried distilers grains with solubles (DDGS) are readily available co-products of ethanol production have been tested with some success in many fish species. Soy protein concentrate (SPC) and fermented soybean meal (FSBM) are products of soybean processing and one of the most promising plant protein alternatives being tested. To determine the use of DDGS, SPC, and FSBM in yellow perch diets, a series of four feeding trials were conducted to determine acceptability, performance, and nutrient utilization. Although the complete nutritional requirements for yellow perch are not yet completely known, experimental diets in these studies were formulated to meet known requirements. The first feeding trial was performed to determine the use of high protein distillers dried grains (HP-DDG; 38% crude protein, 5% lipid) as a fish meal alternative. Four FM replacement levels (25, 50, 75 and 100%) using HP-DDG were blended for comparison with a fish meal control diet. No mortalities were observed during the feeding trial, but significant differences were found in relative growth (F=58.3, df 4, 20, P\u3c0.01), feed conversion ratio (FCR) (F=84.6, df 4, 20, P\u3c0.01), total consumption (F=6.0, df 4, 20, P\u3c0.01), protein efficiency ratio (PER) (F=83.1, df 4, 20, P\u3c0.01), and Fulton condition factor (K) (F=35.0, df 4, 20, P\u3c0.01) with increasing HP-DDG levels. Treatment fish fed ≤50% HP-DDG replacement achieved the best growth performance. Fish fed diets containing \u3e75% HP-DDG replacement failed to reach 100% growth from initial weights. Relative growth of fish fed diets containing 25% HP-DDG 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 FCR were lowest for fish fed diets containing \u3e75% HP-DDG. Dress-out percentage and HSI were not significantly different among treatments and showed no correlation with HP-DDG concentrations. Fillet color was not significantly different among treatments; however, yellowness increased with increasing HP-DDG. Further testing of HP-DDG in combination with supplements is necessary to facilitate increased use by yellow perch