Most dairy units and beef fattening units know exactly what feed they need because they are feeding 365 days of the year , they dont buy fodder unless under extreme circumstances. Suckler and sheep men buy fodder mostly because its not worth carrying over huge amounts of fodder just in case and usually like this year you can buy fodder cheaper than you can make it. It doesnt need to be rocket fuel either, just average is all thats needed. Dairy and beef rations are so complex now that to mess the stock about with bought in fodder could cost thousands in reduced milk/meat yield.Most fodder for sale (cheap or otherwise) is only useful for ticking stock over. It's never going to fatten cattle or make milk without a lot of help.
I must say that I would hesitate in including you in that generalisation, as despite never having seen your bales, we know how you farm.