Many of them partner with farmers, who haul it away, which is a service, and certainly stretches the definition of "free." Like the man said, he had to drive his ass up there, load his truck, and drive back to his farm - all of which involves labor and expense. Jack Daniels, for its part, gets the leftovers of its distilling process removed from its premises. Otherwise it would just pile up and up and they'd have to pay for its removal. So, it's more or less a barter of a good (slop/feed) for a service (removal). Any mid-sized brewery does the same with local farmers.
What happened here is simply that Jack Daniels received a better offer: they get the removal and probably direct payment for the good. A few points, though:
1) The local cattle farmers could not form a collective to counter Three Rivers price.
2) The local cattle farmers assumed that the deal would always be the same, and did not anticipate the threat of the arrangement being superseded by a payment scheme. That's just bad business. They are incompetent businesspeople. I suspect if they had a strong agricultural extension through their landgrant universities, somebody would have trained them to develop a SWOT analysis that included their input costs, but sadly their state universities seem to be more interested in filling football stadiums and eliminating diversity programs. Oh well.
3) The local cattle farmers live so close to their margins that they can't sustain a modest increase in input costs. That's bad business as well. It may also be an effect of tariffs, as beef sales to tariff countries are decreasing precipitously. Hey, they voted for it!
4) Jack Daniels may also be seeking revenue as a result of tariffs. Notably, their markets for US-produced whiskey have collapsed in Canada, previously a giant buyer, and in other areas as well. The tariffs may be forcing Jack Daniels to seek this new source of revenue to fill in the holes left by those collapsing markets.
All of which is to say, nice job, Trumpy! And enjoy, Tennessee!