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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Natural Resource Management

First Advisor

Michael L. Brown


Aquaculture relies heavily on marine-derived fish meal (FM) as a primary feed ingredient. Industry growth, high demand and increasing cost of finite FM supplies create urgency to find alternative protein sources. Plant products having sufficient nutrient composition and no anti-nutritional factors offer a viable alternative to conventional FM based diets. A grain ethanol product stream called distillers grains (DG) offers a potential alternative. DG can be split into two broad classes. Distiller’s wet grains (DWG) are the solids portion of corn material remaining after distillation and centrifugation. Distiller’s dried grains with solubles (DDGS) are produced by mixing the DWG the condensed centrifuge supernatant (aka. Corn syrup), and then drying. A new generation of DG called high-protein distiller grains (HP-DG) adds additional processing to base DG to produce a higher value material with an enhanced nutrient profile. Two Yellow Perch (Perca flavescens) feeding trials evaluated the performance of HP-DG against a fish meal (positive) control and an unconverted DG (negative) control. The first feeding trial evaluated HP-DG’s produced through different processing methods including: fermentation, chemical extraction (CE), and mechanical fractionation (MF). A second trial evaluated HP-DG’s produced through solid state and submerged fermentation processes on both DWG and DDGS substrates. Apparent digestibility of HP-DG’s top performers was also evaluated. Trial one was performed for 16 weeks. Growth metrics and health indices were compiled following completion. The fish meal control showed the greatest relative growth (44437.63 g), while two HP-DG diets; Solid State fermented (SS) DWG (33352.05 g; P=0.21) and SS DDGS (31440.44 g; P=0.37) demonstrated statistically similar performance. Specific growth rate (SGR) followed a similar performance trend, with fish meal (2.01) outperforming all corn-based diets. Submerged fermented DWG showed significantly diminished performance (P<0.01) compared to all other treatments. Survival was not significantly different between groups (P=0.34). SS DDGS and a MF DDGS had the highest survival rates (90%). Visceral fat index (VFI) and spleen somatic index (SSI) were similar across all treatments, while the fillet to weight ratio (approximately 34% of total weight) was greatest in diets containing MF DDGS and CE DDGS. These results show improvement over previous studies using unmodified coproducts, but continued research focused on upgrading co-products is necessary to optimize performance. A second feeding trial compared HP-DG’s created using a solid state fermentation and a submerged fermentation against a fish meal control. A 2x3 factorial design was used to analyze the effect of fermentation technique and base substrate on final growth performance. Growth trial metrics were analyzed upon completion of a 16 week feeding trial. Final relative growth was significantly different between treatments (P=0.03). The submerged DDGS showed the highest relative growth (223±12.8 g) and was significantly higher than solid state DWG (152±6.83 g), but was not significantly higher than the fish meal control (160± 18.2). SGR followed a similar performance trend to relative growth with Submerged DDGS (1.33± 0.04) outperforming all other diets. No statistical significance was detected in SGR (P=0.07) or final tank biomass (P=0.19). Submerged DDGS produced a higher tank biomass (534 ± 32.7g) than all other treatments. Unconverted DDGS (336± 75.7g) and Hybrid DDGS (368 ± 56.5g) produced lower biomass than all other treatments. The submerged fermentation showed more favorable results than the hybrid fermentation, especially in terms of relative growth and FCR. Submerged DDGS showed the highest performance with no significant differences in performance across all administered analysis. All microbially-enhanced products showed increased performance over their base feedstock. HP-DG show significant improvements in performance compared to unconverted DG, thereby creating a competitive advantage in the rapidly expanding markets for sustainable fish meal replacements. Targeting fish species capable of tolerating higher fiber contents will further benefit from the inclusion of HP-DG. With further research geared towards increasing protein values while decreasing fiber content, HP-DG may provide a solution to ease the burden on wild fish populations, and fill the rapidly growing demand for fish protein for human consumption worldwide.


Includes bibliographical references (pages 49-60)



Number of Pages



South Dakota State University


Copyright © 2015 Dustin A. Schulz