What happens to old oxen?

I'm curious to know, what becomes of those old oxen that have served us so diligently in the fields? Do they retire to a peaceful pasture, or do they face a different fate? Is there a system in place to care for them in their twilight years, or are they often discarded and left to fend for themselves? I'd love to hear more about how societies around the world handle the retirement of these hardworking animals.