Blue foods from aquaculture are essential in bridging the protein gap to feed the human population in the future. Recent aquafeed price increases of up to 30% reflect in part the limited raw material basket, and the fact that our drive to extend this basket with novel, more sustainable proteins is only partly successful. Microbial or single cell proteins (SCP) are the frontrunner when it comes to emerging proteins. Two early prototypes of single cell protein with over 50% protein (named here SCP1 and SCP2) were produced by researchers at the DSM Bioscience Centre (The Netherlands) and were tested over a 12-week period in rainbow trout (Oncorhynchus mykiss).
Seven different feeds were produced in a pilot-scale feed mill in Village-Neuf (France). The control diet contained 10% of fish meal and 20% of soy protein concentrate. The two test products were included at 5% (SCP1-5, SCP2-5), 10% (SCP1-10, SCP2-10) and 20% (SCP1-20, SCP2-20) in the diets to replace 5% of the fish meal, 10% of the fish meal and 10% of the fishmeal+10% of the soy protein concentrate, respectively. Each of the seven diets was fed to triplicate groups of rainbow trout (IBW 50g) for 84 days.
Our results show that single cell protein inclusion leads to similar fish performance measured by final body weight as at the end of the trial, performance was similar across the treatments and only the diet formulated with 20% SCP2 showed significantly lower growth (-4.4% compared to the control). The trial’s findings demonstrate a high protein digestibility and amino acid profile, as well as health benefits measured through oxidative burst response. Small differences in protein digestion and amino acid digestion and retention were expected and show that fish metabolism adapted to the new formulations.
The present results demonstrate the potential of incorporating SCP in salmonid aquafeeds up to 20% dietary inclusion, as replacers for traditional ingredients such as fish meal and/or soy protein concentrate. With the move towards the use of environmental criteria in raw material selection, novel raw materials such as single cell proteins can deliver lower footprints, water use, land use and limited impact on bio-diversity. In addition, improving the nutrient quality of the novel ingredients by increasing the digestible protein content, together with the commercial scale-up are needed to extend the raw material basket and deliver sustainable raw materials.