Production of high protein distillersâ dried grains with solubles (HP-DDGS) to replace fish meal in aquaculture diets.

In 2007, wild captured fish accounted for about 15.7% of the animal protein consumed by humans on a global basis, and per capita consumption of fish and shellfish products is increasing, parallel with the global human population. Unfortunately, harvest rates of wild fish have decreased by ~0.7 mmt per year over the past 20 years, and the FAO recently reported that 53% of the world's wild fish stocks are now fully exploited and 32% are over exploited. As a consequence of greater fish demand and the increasing trend of over exploited and depleted stocks, aquaculture production has increased by 9% annually over the last decade. Similar trends of greater demand for and lower wild harvest of fish meal protein have led to a rapid escalation in price of this product. In 2005, 2.7 mmt of fish meal was used in aquaculture feeds, while an estimated 6.7 mmt will be required by 2012. This rate of growth is unsustainable and is reflected in current fish meal prices which are already hampering the economic production of fish and shellfish products for human consumption. Lower cost, more sustainable plant-derived sources of protein have been increasing tested to partially replace fish meal in aquaculture diets. Soybean meal (SBM) has been used to replace up to 20% of total protein in diets for several species, while soy protein concentrate (SPC) has been tested successfully at higher total protein replacement levels. These soybean products provide high protein and relative good amino acid profiles, but are still deficient in some critical amino acids required by carnivorous fishes. SPC can be used at higher levels than SBM, primarily because the solvent extraction process and heat treatment used to produce SPC removes or inactivates undesirable factors. The primary limitations of the current solvent extraction process are its cost, the lack of use for the undesirable components removed in the process, and quality issues that frequently limit inclusion to 50% of total protein in the diet. Corn DDGS has been evaluated in diets at fish meal replacement levels of up to 20%. DDGS has lower protein (28-32%) and more fiber than soy products, but is typically priced at ~50% the value of defatted SBM. Some ethanol plants have incorporated a dry fractionation process to remove part of the fiber and oil prior to the conversion process, resulting in a dry-frac DDGS of up to 42% protein. While this product has been used to replace 20-40% of fish meal in aquaculture feeds, there is considerable market opportunity for an even higher protein DDGS. Prairie AquaTech proposes to convert the fibers and other carbohydrates in DDGS into additional protein using microbial conversion. An constituent byproduct will also facilitate extruded feed pellet formation, may provide an immunostimulant activity to activate innate defense mechanisms that protect fish, and increase corn protein digestibility and absorption during metabolism, providing higher feed efficiency and yields. We anticipate this microbial treatment process will provide a valuable, sustainable aquaculture feed that is less expensive on a protein basis than SBM, SPC, and fish meal.