A cow down for days should have been seen and shot by the owner if nothing else. There aren't too many places, thankfully, that are so insane that a farmer can't put down livestock intended for food. Where we live I sometimes help animal control document cases. Unfortunately what you saw is not uncommon. Most notable case here lately was a man who just let a herd starve because he didn't have the money for feed and the graze ran out, sixteen had died, another 14 dying, he just ignored them as his fields filled with dead cattle. But one cow, or two or four, not even particularly noteworthy as a case goes. Of course they're also ignoring the livestock dogs, who are also not being fed but who live awhile longer on the dying livestock. Unless the moron has penned them up because they've been getting out, looking for food and drawing attention to the place. The record for penned and dying great pyrenees this year so far was 24. I really would rather not see that number topped.
Some folks keep livestock well and reasonably and provide a humane end instead of a vet, and that's okay. What the OP saw, Letting it die for days downed and suffering in it's own s--- pile is not right but it's done all the time. Some people care. Some don't. Laws don't make anyone care. You care, or you don't. Your're responsible within your means, or you aren't. Can't feed it, sell it or kill it humanely. But a slow death by starvation and disease... just because someone can't be bothered... In my opinion it's wrong, but opinions are exactly like .......holes, everyone has one and no one like's anyone else's.