Nephrocalcinosis or kidney stones is one of the key production challenges in Norwegian salmonid hatcheries. In 2022, nephrocalcinosis was ranked as the second highest cause of mortality, poor fish welfare and reduced growth in Norwegian hatcheries, and as the challenge that increased the most during 2022.
Nephrocalcinosis is the deposition of mineral salts in the excretory tubules of the kidney. It is found in both hatcheries and in seawater farms. Based on a recent survey, it is estimated that up to 60 million fish put to sea in 2021 would have been affected by nephrocalcinosis resulting in economic losses of over 500 million NOK. This project aims to develop a diet to mitigate the effects of nephrocalcinosis on the health and welfare of salmon. It will build and expand upon existing knowledge about nephrocalcinosis at the whole fish, organ and cellular levels. Nephrocalcinosis will characterised at different stages of fish development in a commercial hatchery, and biomarkers associated with the condition identified. A model will be developed to cause nephrocalcinosis for the purpose of testing different diets against the progression of the condition. Lastly, a prototype diet will be evaluated against nephrocalcinosis at a commercial hatchery. This project will contribute towards improved fish welfare and the sustainable production of more fish biomass at lower cost and with a lower carbon footprint.
Nephrocalcinosis was evident grossly and microscopically in the commercial hatchery when the fish reached 40 g. The prevalence of nephrocalcinosis, and both gross and microscopic damage worsened with time. In the model development experiment, the combination of exposure to high carbon dioxide levels in the water, and to diets containing high levels of mineral salts resulted in gross and microscopic damage to the kidney, and alterations in several blood and urine parameters. More research is needed to optimize the model and to investigate the mechanisms behind these results before diets can be tested.
Nephrocalcinosis or kidney stones is one of the key production challenges in Norwegian hatcheries. In 2022, nephrocalcinosis was ranked as the second highest cause of mortality, poor welfare and reduced growth in Norwegian hatcheries, and as the challenge that increased the most during 2022. Nephrocalcinosis is characterised by the deposition of mineral salts, mainly calcium, and to a lesser extent, magnesium, in the excretory tubules of the kidney. It occurs in flow through and recirculating aquaculture system (RAS) hatcheries, and in sea water farms. Based on a recent survey it is estimated that up to 60 million fish put to sea in 2021 would have been affected by nephrocalcinosis resulting in economic losses of over 500 million NOK. This project aims to develop a diet to mitigate the effects of nephrocalcinosis on the health and welfare of salmon. It will build and expand upon existing published and unpublished knowledge about nephrocalcinosis and osmoregulation at the whole fish, organ and cellular levels. Nephrocalcinosis will be identified and characterised at different stages of fish development in a commercial facility to identify biomarkers associated with the condition. A model will be developed to induce the development of nephrocalcinosis so that different diets may be evaluated against the progression of the condition. Lastly, a prototype diet will be evaluated against nephrocalcinosis at a commercial facility. This project will contribute to improved fish welfare and the sustainable production of more fish biomass at lower cost and with a lower carbon footprint.
