Evaluating the nutritional potential and microbiome effects of feedinga brewery protein isolate as an alternative to insect meal when fed to Atlantic salmon.
In this study the net protein losses associated with feeding black solider flies (BSF) with brewery waste to produce an insect meal versus producing a protein isolate from such brewery waste using isoelectric precipitation methods were modelled. Following that modelling exercise a brewery protein isolate (BPI) was prepared which had protein levels of 470 g/kg which represented an 80% yield efficiency of the protein and was higher that the BSF meal (395 g/kg). Both the BPI and BSF and a soy protein concentrate (SPC), were then fed to post-smolt Atlantic salmon (Salmo salar), to compare their nutritional qualities. In addition to the characterisation of the composition of each test ingredient, the digestibility and palatability as well as microbiome effects of each ingredient was assessed using a diet-substitution digestibility study approach. For this each of the BPI, BSF, and SPC were included in test diets at 30% inclusion with 70% of each diet coming from the same basal mash. A reference diet was prepared using the same feed preparation methods but based on 100% of the basal mash. Each diet was fed to a tank of thirty-five salmon for a one-week acclimation period before being stripped of faeces, after which the process repeated twice more to generate three replicates through time.