Two of the global Sustainable Development Goals (SDG) are to achieve food security and improved nutrition (SDG 2), and to conserve marine resources (SDG 14). In the last years, per capita fish consumption has almost doubled, increasing the demand for fish. Aquaculture is anticipated to cover 62 % of this demand by 2030. But since feeds rely on marine-origin components, this adds extra pressure on wild fish stocks already strained by rising global demand.
To make fish farming more sustainable—both environmentally and economically—producers have started using less marine-based ingredients in fish feed. Instead, they’re turning to specially formulated feeds made from new, alternative raw materials. These feeds must still deliver top-quality nutrition to ensure healthy fish and rapid growth. In fact, better feeds and additives are now seen as key to improving fish health, welfare, and overall performance in aquaculture.
Right now, the most common way to evaluate new feed ingredients or additives is through live fish trials, known as vivo studies. Although physiologically relevant, in vivo trials have ethical and practical disadvantages, as they are time-consuming and costly. In vitro assay—lab-based tools that use cells instead of live animals— are suggested to reduce harm by replacing traditional in vivo trials. Today, these models are built using fish cell lines. By applying in vitro assay, researchers can indirectly study how new feed additives or bioactive compounds affect fish health, without needing to assess on live animals.
The project successfully established the in vitro assay using the gut, gill, and liver cell lines from trout. The cells were analyzed for cell viability, ROS production, wound healing, and mitochondrial membrane potential (MMP) when exposed to feed ingredients. The method was applied with ingredients present in one of the commercial feeds produced at Skretting. The results published in a scientific journal showed that in vitro assays were a useful tool for screening functional ingredients and provided information about the ideal ranges for feed components. These findings suggest that this method could help fine-tune the concentrations of the ingredients in future feed diets. At the same time, the project contributes to increasing knowledge of nutrition and health, particularly on the interaction between feed compounds and their absorption by cells. Then, a validation was performed to assess the sensitivity of the in vitro assay by comparing astaxanthin encapsulated from three diverse sources.
After establishing the in vitro assay, a feeding trial (in vivo) was performed to correlate the in vitro data. The animals were fed with feed with astaxanthin in three different concentrations, and the fish samples were collected at the end of the feeding trial. The results suggested that in vitro assays could be a useful tool for predicting in vivo physiological outcomes due to dietary interventions. And contributed to building expertise on in-vitro in-vivo correlation methods that potentially can be applicable for aquaculture.
In vitro assays are a powerful tool to understand molecular and cellular responses when testing feed ingredients, although they possess certain limitations. This assay directly contributes to developing new diets and reducing the time and number of animals used for testing new diet formulations. The outcome of the PhD project provides a valuable foundation for further research at Skretting and alternative solutions to the aquaculture sector that enable the salmon industry to expand sustainably without compromising fish health and welfare.
This project aimed to enhance the efficiency of early-stage evaluations of feed ingredients, minimize dependence on animal testing in accordance with the 3Rs principle, and provide a robust framework for assessing the biological effects of ingredients.
Cell in vitro screening was used to assess the functionality of ingredients. This method elucidates the molecular and cellular mechanisms by evaluating cell proliferation, oxidative stress response, wound healing behaviour, and cell toxicity. Moreover, an animal trial was performed to investigate the correlation between in vitro and in vivo findings.
Cell in vitro screening has been demonstrated to be a powerful tool to understand molecular and cellular responses when testing feed ingredients, although it has certain limitations. To address the inherent limitations, more physiologically relevant models, such as co-culture and organoids, could be employed to better align with in vivo conditions.
The Atlantic salmon (Salma salar) aquaculture has increased intensely in recent years alongside the culture of other fish species and has become one of the fastest-growing food-producing sectors. To ensure production growth improvements in fish growth and health are essential. The elaboration of new feeds, using novel raw materials, needs to ensure that both fish and final products are of the highest quality. Currently, in vivo trials are the most common strategies to study the effect of new protein sources or feed additives, and more sustainable alternatives are highly needed.
Furthermore, Ax is widely used for flesh pigmentation of salmonid fish, and at present, it constitutes a major part of the feed cost. Beyond this, Ax could have other physiological functions, such as being an antioxidant or a precursor of vitamin A. To this aim, nanotechnology has emerged as a powerful means of encapsulating, protecting, and delivering bioactive substances in foods, thereby improving their efficacy. These nanoscale delivery systems should be constructed entirely from food-grade ingredients and should be designed to provide resistance against the elevated temperatures, light levels, and oxygen levels they may be exposed to during food processing and storage.
This industrial PhD project will contribute to increasing the knowledge on nutrition, encapsulation, and health, in particular on the interaction between feed compounds and their absorption on cells. An in vitro system will be developed to screen novel ingredients or bioactive compounds. This will directly contribute towards the development of new diets and reduce the time and number of animals used for testing new diet formulations. The outcome of the PhD project will provide essential solutions to the aquaculture sector that enable the salmon industry to expand in a sustainable manner without compromising fish health and welfare.
