Sustainable Trout Aquaculture Intensification (SusTAIn)

Funding Agency: Niedersächsisches MWK
Involved Institutions Faculty of Agricultural Sciences, Georg-August-University Goettingen and Institute of Parasitology, University of Veterinary Medicine Hannover Foundation
Project Period: 2017-2021
Budget: in total 756,000 Euro

Project Aims

The genetic adaptation to changing environmental conditions, e.g. changing feed is a key in the evolution of fish populations with high interest for the aquaculture sector. Especially when looking at the context of changing commercial feed compositions in the last years. High shares of fishmeal and fish oil in the diets of farmed fish are one of the causes for the unsustainable management and the overfishing of global fishing grounds. The substitution of large feed shares by plant-based alternatives is often found to have negative effects on carnivorous fish like trouts. Common consequences are lower growth rates, health and welfare issues or decreased environmental efficiency.
The SusTAIn project therefore uses the genetic variability and adaptability to innovative feeds to get new insights into possible sustainable intensification strategies. Consequences for welfare and environmental issues are researched in detail. Four working packages focus on different aspects to achieve a comprehensive picture on the topic.

The work package 1 “Breeding for adaption” aims to create site-adapted fish breeding lines and genotypes with high adaptation to fish meal alternatives and robust immune status. Quantitative genetic approaches, i.e. a classical genetic evaluation using the information of the relatives are combined with state-of-the-art high-throughput methods for the investigation of the transcriptome (RNA-seq). We aim to reveal basic mechanisms of adaptation to a modified diet without fishmeal for carnivorous trout and possible biomarkers for selective breeding.

The Fish Disease Research Unit at the University of Veterinary Medicine Hannover contributes to “SusTAIn” with work package 2 “Animal welfare and animal health”. Our task is to study a possible impairment of animal health by alternative feed ingredients. For this we will assess possible damages to skin and fins as well as the expression of heat shock protein 70 (HSP 70) in gill, skin, liver and gut samples by ELISA. HSP 70 responds to different parameters of the rearing system, an increased expression, however, is generally regarded as an indicator of chronic stress in the fish. In order to analyse, whether the alternative feed ingredients used might cause an intolerance in rainbow trout, samples from the anterior and posterior gut will be collected and evaluated by means of histology for the occurrence of pathological changes. In addition, molecular indicators for a modulation of the infection barrier of the gut mucosa will be investigated in samples from the same localisations. For this, the expression of genes encoding transmembrane proteins (e.g. occludine, desmocollin), anti-microbial peptides, as well as markers for inflammatory responses (IL-1, iNOS, TNF alpha) will be investigated. Furthermore we will investigate whether alternative feed ingredients might affect the disease resistance of rainbow trout. Tissue samples of fins, gills, and scales from the different trout populations and feeding regimes will be investigated in vitro for the susceptibility to infections with Yersinia ruckeri (bacteria causing enteric redmouth disease in rainbow trout) and VHSV (viral hemorrhagic septicemia virus). The susceptibility of rainbow trout from the different feeding regimes to an infection with VHSV will be validated in a subsequent infection experiment. The aim of these investigations is to safeguard animal welfare and animal health in rainbow trout fed with a diet containing alternative feed ingredients.

The work package 3 „Nutritional physiology“ intends to formulate model diets for rainbow trout, where fishmeal is substituted by the alternative feed ingredients partly defatted insect meal (Hermetia illucens) or microalgae meal (Arthrospira platensis). Diets will be evaluated for feed acceptance, growth response of fish as well as technological factors of feed manufacturing. For selected strains of rainbow trout (local and commercial), the nutrient utilization (especially protein) is quantified and protein quality of the model diets will be evaluated. Furthermore, effects on fish body composition (e.g. fatty acids), parameters of digestibility as well as intestinal morphology and health status are investigated. Results will provide a database for evaluating the genetic variation of the adaptive potential to make efficiently use of high inclusion rates of alternative feed proteins in mixed feeds for trout. Finally, the sub-project will significantly contribute to a more sustainable intensification of trout aquaculture by implementing fishmeal free feeding concepts.

Working package 4 "Environmental and technical efficiency" is going to conduct a farm survey in northern Germany to determine the status quo of production and regional differences. The main contribution to the project comes from the examination of the practicability of the developed intensification strategies on the farms. Key theses to be studied are possible improvements to the profitability of the enterprises, the potential for improvements in regard to environmental and animal welfare issues and cross effects due to organisational adaptations to the changing feed components. Other factors which hinder the sustainable intensification are also conducted and analysed. The final task is to estimate the consequences for the enterprises and the societal benefit.

Sustain Gruppe
group of project leaders and staff, February 2018