Acute Stress Response in Rainbow Trout (Oncorhynchus mykiss) Fed Bioprocessed Soybean Diets

The use of plant-based proteins to replace marine-derived fish protein (MDFM) has gained interest for reducing feed costs.  As a result of bioprocessing, additional fish health benefits may be derived from these ingredients. Stress is a common concern for many culturists, and an ongoing 60-day feeding trial is currently evaluating physiological changes from acute stressors in rainbow trout (Oncorhynchus mykiss) fed bioprocessed soy-based diets.  Experimental diets contained two bioprocessed soybean meal levels (25% and 35% inclusions) and a commercial soy protein concentrate (25% inclusion). Dietary controls included a fish meal (FM) reference and an unprocessed soybean meal (25% inclusion). Juvenile rainbow trout (42.3g) were stocked at 15 fish/tank in a 30-tank recirculating aquaculture system and fed 2% of body weight for the 60-day trial.   Naïve rainbow trout were sampled on day 0 for baseline levels of cortisol, blood glucose, hematocrit, and macrophage respiratory burst activity. On days 30 and 60, 5 fish per tank will be subject to 4 hours of acute stressors (low flow rate, decreased oxygen, handling stressors) or left unstressed as a control group. Continued assessment of novel plant-based ingredients to reduce stressors may benefit producers when determining optimal stocking rates or transporting fish.