Lets say, just hypothetically, that this is implemented at a federal government level. Further, lets take as a given that this supplement makes cows healthier, happier and cheaper to feed. Additionally, lets assume that we want this enough to subsidize this for farmers to the point that they're actually paid slightly to implement it. I'd call this set of givens the ideal situation.
Even if we had such an ideal situation, there will be a lot of ranchers and farmers who don't trust the government's plan (my father will probably be one of them) and people in that group won't implement the change. Then there will undoubtedly be the "organic" beef people who demand 3NOP free labeling and some farmers and ranchers will target that market and not implement. Other countries won't necessarily follow suit. Some will, but some certainly won't.
However, knowing that some people will resist change isn't a valid reason to avoid considering whether change needs to happen. Civil rights, the abolition of slavery, freeing jews in internment camps... all are changes that every normal person now would agree needed to happen. There was resistance at the time and there are still people who don't like the changes even now, but that doesn't mean we shouldn't have put the effort in.
Change is bad. Not changing is bad. No matter how elegant and beneficial a solution is, no matter how bad the problem is, there will always be some struggle implementing the solution. Even knowing leaded gasoline is bad, and having some idea how bad, there are still quite a few engines (small planes jump to mind) which still use it. Changing to unleaded gasoline was beneficial and a struggle, and it was worth it. (Do some reading if you are unfamiliar with how significant that change was.)
My point is that we can acknowledge there will always be issues with implementing big changes without weakening the argument that change is good and needed.