In Finland the results research shows that microalgae are a suitable substitute for soybean meal and faba beans in dairy cow nutrition. Studies show that there are no biological or physiological constraints for protein feed use of microalgae. Microalgae are slightly inferior to rapeseed meal as indicated by results of milk production and N utilisation. The greatest challenge limiting the feed use of microalgae for lactating dairy cows is their poorer palatability relative to conventional feeds. Also the production costs of microalgae are so far too high.