135 Production of a fifty percent functional protein concentrate from the dry grind ethanol process and use of the product in diets for Atlantic salmon

Abstract

Abstract The corn distilling industry is a major processor of grain, but the high fiber co-product (DDGS), has limited application in feed. Simple mechanical stillage separation downstream of fermentation produces a high protein (52.4 % DM), highly digestible, low crude fiber (4.4% DM) product containing approximately 25% DM spent brewer’s yeast (high density distillers’ protein: HDDP). Currently, approximately 300 ktons of HDDP are produced annually in the USA, and the volume will double in 2020. The effect of graded inclusion levels of HDDP on growth, feed efficiency, nutrient utilization, blood chemistry and gut histology of 525 post-smolt Atlantic salmon (initial body weight 304 ± 10.7g), randomly allocated to three tanks per treatment, was tested in a salt-water recirculating aquaculture system. One control diet with no HDDP was formulated to meet the nutrient requirements of Atlantic salmon. Four test diets were formulated to contain graded levels of HDDP at 5, 10, 15 and 20% respectively. HDDP partially replaced soy protein concentrate and corn protein concentrate in the diets. Salmon were hand-fed to satiety, 3 times daily during the 84-day trial. Throughout the trial the performance of fish on all treatments exceeded commercial growth rates with thermal growth coefficients (TGC) in excess of 0.160 and feed conversion efficiency of ≤ 1.0. Overall HDDP was a nutritious feed ingredient and had no significant impact on performance. Overall TGC was highest (0.200 over the 84-day trial period) in fish fed the diet containing 10% HDDP. Both villi length and villi width in the distal intestine of salmon fed diets containing HDDP tended to be higher than in the controls. Overall, HDDP derived from the dry grind ethanol process was a safe and nutritious novel feed ingredient for Atlantic salmon, and the potential beneficial effect on gut morphology merits investigation.