Growth, proximate composition, and sensory characteristics of Rainbow Trout Oncorhynchus mykiss consuming alternative proteins

• Our study compared the effectiveness of multiple plant and animal-based feeds, simultaneously, to grow Rainbow Trout.
• We also compared the effectiveness of two different feed protein: lipid ratios (45:20 and 40:20 P:L) to grow Rainbow Trout.
• Our results allow fish culturists to select appropriate feeds based upon cost, fish growth rates, and consumer acceptance.

Increases in the price of fishmeal have spurred increases in the cost of aquafeeds to fish production facilities. This intensified a search for alternatives to fish meal. In this study, eight experimental aquafeeds were formulated from 4 ingredient groups that excluded fishmeal. These ingredient groups were designed as an animal product diet (APD), a novel plant protein diet (NPD), a plant products with future potential diet (PFP), and a plant product diet (PPD). These diets were compared to two standard fishmeal based diets (FMD). Each ingredient group was formulated into high protein (45%) and low protein (40%) diets and used in a 5 × 2 factorial feeding trial. Diets were randomly assigned to three replicate tanks containing 15 juvenile Rainbow Trout Oncorhynchus mykiss (mean initial weight = 91.3 g). After the growth trial fish from each treatment were used in a sensory analysis, examining the aroma, flavor, and texture of the fillets being harvested. The 40% protein FMD produced both the highest final wet weight: 441 ± 5.7 g (mean ± SEM) and lowest feed conversion ratio 0.93 ± 0.02 g feed consumed/g weight gain (mean ± SEM). However, the best performing experimental diets had comparable values. More differences in growth metrics were noted among different feed ingredient groups than between protein levels. Proximate analyses were also used to determine proportions of moisture, protein, lipid, and energy within a subsample of fish from each treatment. These analyses indicated protein sparing and lipid sparing by fish consuming the 40% protein diets and 45% protein diets, respectively. Sensory analyses identified few significant differences in fillet characteristics among the different treatments. The results indicate that diets composed solely of plant-based ingredients can promote similar rates of Rainbow Trout growth, produce high quality fillets, and be less costly to fish producers.Statement of relevanceWe show that alternative feeds efficiently grow trout.