Acronym

L4-60175

Department:

Department of Animal Science

Type of project

ARIS projects

Type of project

Aplikativni

Role

Lead

Duration

01.01.2025 - 31.12.2027

Total

1,03 FTE

Project manager at BF

Sušnik Bajec Simona

Research Organisation Partners

  • University of Ljubljana, Biotechnical faculty
  • AlgEn d.o.o.
  • Fisheries Research Institute of Slovenia 
  • Emona d.o.o.
  •  

Co-financing Organisation

  • Ministry of Agriculture, Forestry and Food
  • Jata Emona d.o.o.
  • Tanin Sevnica d.d.

 

Abstract

Many salmonid species are becoming threatened due to climate change, habitat degradation, overfishing etc. To prevent a population-decline and maintain genetic diversity that is essential to the long-term survival of a species, female brood stock and wild males should be used to produce progeny to be stocked into the wild, using only fertilized eggs to avoid hatchery favoured fish. A vital brood stock is, thus, a prerequisite for production of high-quality gametes. Nutrition is one of the key factors in fish reproduction, growth and health, so to ensure and maintain the desirable reproductive capacity and effective immune response of the broodstock, the selection of suitable feed is of crucial importance. A high proportion of fish feed is still made from fishmeal, which comes from the catch of fatty blue marine fish, so its composition is much different from that which is typical of the natural food of obligate freshwater salmonids, such as e.g. grayling (Thymallus thymallus). In the last few decades, various alternative sources of protein and fat, mainly vegetable, have been introduced into fish feed, with multiple disadvantages. In recent times, more suitable alternatives are being sought, such as, for example, insects, with a high content of proteins, fats, vitamins and minerals, and algae, which, through their beneficial effect on the intestinal microflora, have been proven to have a positive effect on many physiological processes related to the immune response.

As part of the project, we will focus on preparation of new feed mixtures for grayling, which will include sustainable sources of nutrients, namely insects (black soldier fly) and microalgae (spirulina), i.e. groups of organisms that represent a high proportion of grayling's natural diet. The model species will be grayling due to the following reasons: (1) grayling is one of the most endangered salmonid species that requires intensive protection for its survival, (2) grayling is a very demanding and sensitive species for breeding with very specific requirements; high mortality compared to other salmonids is reported for all life stages, their reproductive parameters are suboptimal - and yet there is no specifically optimized feed mixture for this species, (3) we have already made comparisons between wild and farm-raised grayling females according to biochemical composition of eggs and found differences between two groups, especially in the ratio of fatty acids. Since many authors report that feed composition for fish broodstock should be based on biochemical composition of eggs in natural populations, we conclude that existing feed, which was primarily designed for the diet of anadromous rainbow trout, is probably far from optimal for the diet of grayling.

In the project, we set three hypotheses: (1) we assume that the composition of the feed with which grayling is currently fed is not suitable for this species, and that it represents one of the reasons why the reproductive and immune parameters of farmed grayling are suboptimal; (2) ) we expect that the feed mixture, in which we will replace a certain proportion of proteins of fish and plant origin with black soldier fly meal and spirulina, will improve the reproductive performance of farmed graylings, reproductive parameters and mortality of embryos, and the quality of eggs, which will be determined through biochemical composition and transcriptome; (3) we expect that the change in the composition of the feed mixture will also improve the immune status of farmed graylings, which will be determined through changes in the immune genes expression, the maternal transfer of immune components to eggs and the structure of the gut microbiome. 

 

The phases of the project and their realization

 

The project is methodologically divided into five work packages (WPs), with additional sub work packages, each one covering specific method.

WP1 Coordination: WP1 will ensure efficient and cost-effective project management, reporting to all involved funding agencies, and co-ordination among the project partners. Regular dissemination meetings will be organized. Knowledge generated will be disseminated by ensuring timely presentations at scientific and professional conferences and writing of peer-reviewed articles. Project consortium will closely adhere to the open science practice to secure a broad accessibility of all resulting studies and datasets.

WP2 Diet formulation and feeding experiment design: Four novel diets for grayling will be developed: a basic feed that covers the specific nutrient requirements of grayling broodstock and three experimental feeds with added spirulina and BSF. Feeding experiment will be designed, considering the four experimental groups with duplicates, and the amount of feed needed and supplied to the fish according to the fish mass. The feeding trial is a crucial first step in the overall project, which will allow the experimental fish to be acclimatised to diets with added spirulina and varying amounts of insects as a substitute for fishmeal and plant based protein sources.

WP3: Sampling and measurements: sampling and measurements of broodstock, gametes and larvae in each of the experimental group will be performed to determine the influence of novel diet on the immune status and reproductive performance of grayling. Samples will be further analysed (WP4) and statistical analyses performed to test for the influence of experimental diet on the immune status and reproductive performance of grayling. Correlation between different variables will be assessed (WP5).

WP4: Biochemical, immunological and genetic analyses: The influence of experimental diet on the immune status and reproductive performance of grayling will be assessed using different multidisciplinary laboratory approaches, including gas-chromatographic, immunological and molecular analyses.

WP5: Influence of novel feed ingredients on immune status and reproductive performance of grayling: Within this WP results of all analyses and measurements will be integrated with the aim to determine how newly formulated diet including spirulina and BSF influences immune status and reproduction performance in grayling. Results of multidisciplinary analyses interplay between different parameters including direct and indirect influence of diet will be assessed and hypotheses tested.