Abstract

A major challenge for the aquaculture industry is the supply of sustainable feeds. A promising model to achieve this is to utilize circular flows where feed ingredients, such as single cell protein, are cultivated using side streams of the food industry. The aim of this study was to evaluate the marine yeast Candida sake, produced on herring brine side streams, as a source of protein and immune stimulant in feed for salmonid fish. The dry C. sake product contained 54% protein (3.3% lysine and 0.8% methionine) and 13% lipids (1.1% eicosapentaenoic, EPA, and 1% docosahexaenoic acid, DHA). Four experimental diets were designed and tested in a 9-week feeding trial using juvenile rainbow trout (Oncorhynchus mykiss). A control diet containing both fish and plant-based ingredients constituted the base feed to which 20% (to evaluate effects on digestibility, growth and intestinal physiology), 20% heat-treated (to evaluate effects of downstream processing) and 3% (to evaluate immune stimulatory properties, replacing 3% soy protein concentrate) C. sake was added. The apparent digestibility coefficient of C. sake for protein, fat and gross energy was above 80%, and for amino acids above 90% regardless of treatment, suggesting a high bioavailability of C. sake. All three yeast containing diets performed equally to the control regarding specific growth rate, feed conversion ratio and functional intestinal health. These results suggest that C. sake is a promising alternative protein source for circular feeds in the salmonid industry. The presence of EPA and DHA represents an added value. The heat treatment increased the apparent digestibility coefficient of dry matter by 8% but decreased amino acid digestibility by on average 3%, indicating that heat treatment may not be the optimal downstream processing technique. Furthermore, the inclusion of 3% C. sake increased the intestinal lamina propria width and TGF-beta transcription, indicating an immune stimulating effect. Future research is needed to understand these immune modulatory effects of C. sake supplementation.

Keywords

Aquafeed; Immune stimulation; Intestinal health; Circular economy; Alternative protein

Published in

Aquaculture
2023, Volume: 571, article number: 739448
Publisher: ELSEVIER

SLU Authors

• Langeland, Markus

  • Department of Applied Animal Science and Welfare, Swedish University of Agricultural Sciences
    
  • RISE Research Institutes of Sweden
  • University of Gothenburg

Sustainable Development Goals

SDG14 Conserve and sustainably use the oceans, seas and marine resources for sustainable development
SDG2 End hunger, achieve food security and improved nutrition and promote sustainable agriculture


UKÄ Subject classification

Fish and Aquacultural Science


Publication identifier

DOI: https://doi.org/10.1016/j.aquaculture.2023.739448

Permanent link to this page (URI)

https://res.slu.se/id/publ/122032