Brewery byproducts, brewer’s spent yeast (BSY, Saccharomyces cerevisiae) and brewers spent grains (BSG), have little-to-no economic value, as they have little conventional usage outside of disposal; however, if a novel process is applied, the valuable nutritional properties of the byproducts could be utilized by the aquaculture industry as a beneficial feed additive. Specifically, the byproducts can serve to enhance the health and growth of rainbow trout (Oncorhynchus mykiss), which are both economically valuable and a model species for other salmonids. Application of brewer’s byproduct were performed via top-coating directly onto commercial feed, and both BSY and BSG underwent novel processing and were provided to this study.
The aim of this research was to determine if processed BSY, and black soldier fly larvae (BSF) cultured on BSG, could enhance the health and production of farmed rainbow trout in correlation to their intestinal bacterial community structure. Fourteen juvenile rainbow trout (28.6 ± 0.4 g, mean ± standard error) were stocked per polyethylene tank across 24 tanks (170 L each) in a single recirculating aquaculture system (RAS). The treatment groups for BSY were performed in quadruplicates at the tank level, while for BSF was performed in triplicates. Over the eight-week trial, compared to the control, all diets grew significantly (P < 0.01**, Table 1.) faster than the control while also having decreased feed conversion ratios (FCR). Moreover, there were no significant differences of intestinal bacterial community structure between treatment diets and the control, implying no dysbiosis due to the altered diets. Overall, the supplemented byproduct diets served as an effective growth additive for the trout without negatively impacting health