Forsøksdyr: FoN Zf Infection 2

Godkjenningsdato 03.11.2020

Godkjenningsperiode 03.11.2020-31.12.2022

The SFI "Foods of Norway" is developing experimental diets for farm animals and fish using sustainable local feed ingredients to reduce the reliance on imported feed ingredients. These experimental diets contain varying levels of protein derived from yeast that are produced from sugars and other nutrients derived from natural resources such as wood, grass and seaweed. The goal of Foods of Norway is to evaluate the potential of new, yeast-based diets to replace at least partially currently used soybean-based feeds, and to evaluate the potential of certain yeast strains to promote resistance to bacterial infections.

1 Purpose
The purpose of this project will be to evaluate the potential of zebrafish and medaka as infection models for the salmon pathogen Aeromonas salmonicida and to assess the performance of yeast-containing diets in the zebrafish infection model.

2 Distress
A low mortality infection model will be used. Fish will be exposed to level of bacteria that results in less than 20% mortality. Surviving fish would experience moderate distress. Moribund or fish experiencing severe distress are to be euthanazed in accordance with defined humane endpoints.

3 Expected benefit
It is expected that the effective screening in zebrafish and medaka will greatly enhance the identification of the health-related bioactivity of diets. The benefit will be that fewer diets (but with a known bioactive profile) are tested in production animals and fish. This will reduce the number of large animal experiments that need to be performed

4 Number of animals, and what kind
The project will use 1350 zebrafish and 360 medaka. The initial infection experiments will be performed to compare directly the virulence of Aeromonas salmonicida in zebrafish and in medaka, in the latter at 2 different temperatures (20°C and 12°C). In each experiment, surviving fish will be collected at 1, 2 and 4 weeks after infection for (a) group weighing, (b) histopathology analysis, (c) immunohistochemistry analysis using an antibody specific to Aeromonas salmonicida, (d) qPCR analysis using primers specific to inflammation and infection response markers as well as to Aeromonas salmonicida.

The diets to be tested in the zebrafish infection model are: 6 different diets with different yeast-based ingredients, in comparison with 1 standard zebrafish diet. Adult zebrafish will be fed for 4 weeks, and will be challenged with bacterial infections (Aeromonas salmonicida) after 4 weeks, after which survival rates will be determined. Surviving fish will be sacrificed at 1, 2, and 4 weeks after infection, after which they will analyzed as described above.

5 How to adhere to 3R
Based on the results of these experiments, future studies of yeast-based diets in zebrafish and/or medaka will be designed accordingly to minimize the number of animals used in each study.