I made a couple of them out of drill stem and sucker rod, one held 2 bales, the other 4.
Found them a PITA in the end, cows were digging trenches around them unless i moved them after every couple feedings, in wet weather it became mud holes.
In winter they froze down even though they were on skids
I sold them, i pity the guy that bought them
One is better off to feed the bales in the field and never on the same spot, that way they spread the turds them selves and one don't have to clean corrals either