The government and our largest dairy co-operative have been looking into seaweed for a while now and it looks like production of seaweed cow feed is about to get underway:
https://www.rnz.co.nz/national/programmes/ninetonoon/audio/2...
“Salmon is an example and you are restricted on the basis of the nitrogen output of those fish. If seaweed, asparagopsis in this case, is planted downstream, one of the foods it likes to eat is nitrogen."
That's science. Sounds like good work. Hopefully they can overcome the seaweed cultivation obstacle mentioned.
If a cow doesn't like something it won't eat it unless it is all you feed it. They are pretty deft at picking around stuff they don't like. (They do this when grazing too) As I understand it, the seaweed is just a supplement added to the silage and they voluntarily eat it when it's supplied.
Cows aren't picky eaters. There was once a case where one was caught eating a python. But again, they are all unique individuals just like people. Some like stuff that others don't. Some get neurotic and eat rocks and dirt. I'm sure there are a quite a few cows that don't like seaweed but eat it anyways just for something to do.
https://www.abc.net.au/news/2020-10-28/cow-eating-snake-phot...