DIETARY EFFECTS OF FEEDS SUPPLEMENTED WITH MACROALGAE EXTRACT AS A SOURCE OF VITAMIN K1 IN SENEGALESE SOLE Solea senegalensis GROWTH AND SKELETOGENESIS

Macroalgae have recently started to be used in fish feeds, as an added‐value dietary ingredient since they are good sources of both novel biologically active substances and essential compounds ¹. A balanced vitamin dietary content is crucial for optimal fish growth and to ensure a correct formation of the skeleton, therefore minimizing skeletal deformities. The onset of skeletal deformities occurs during early life stages of fish larvae and will have negative impacts on survival, growth and quality of the aquaculture produced fish. A previous study showed a reduction on the incidence and severity of skeletal deformities in Senegalese sole (Solea senegalensis) when larvae were fed enriched Artemia supplemented with 250 mg/kg of vitamin K1 (phylloquinone; VK1)². Since macroalgae are known to have high VK1 contents³, and Plocamium cartilagineum presents 1000 mg/kg of VK1, we have prepared ethanolic extracts from P. cartilagineum (1000 mg/kg VK1) as a natural source of VK1 to be used in sole larval feeding.

Methods: P. Cartilagineum was collected by snorkelling in the lagoon system of Ria Formosa (Algarve). After collection the algae were rinsed with fresh water and freeze dried. Ethanolic extract was prepared from 500 g of dry algae and VK1 contents determined by UPLC. The extract was added to Red Pepper for achieving 250mg/kg VK1 and Artemia metanauplii was enriched (12h + 1h) prior to feeding. Sole larvae were fed enriched artemia (Control and VK1 250) from 10 to 40 dpf. Survival, growth, VK1 contents and skeletal deformities were evaluated.

Results and conclusion: No effects were observed both in survival and in growth from feeding the sole larvae with P. cartilagineum VK1 extract enriched Artemia. Sole larvae fed enriched Artemia supplemented with 250mg/kg VK1 showed significantly higher levels of VK1 than the control larvae. The evaluation of skeletal deformities revealed a reduction in the skeletal deformities of the group fed with enriched  artemia supplemented with VK1 rich P. cartilagineum extract. Further characterization of the extract is necessary to establish the chemical profile.

References: 1-Wan et al 2019. Rev. Aquac. 11: 458-492; 2-Richard et al 2014. Marine Biotech. 16, 522-537; 3-Kaila 2015. PhD thesis

Acknowledgements: This work was co-financed by the European Maritime and Fisheries Fund (EMFF/FEAMP) through the National Operational Programme MAR2020 (grant ALGASOLE-16-02-01-FMP-0058); and by the FCT (grant UID/Multi/04326/2019).