Your calf may have a hernia.
We had a calf that we bought at the auction.
Young calf , Actually one of our first one's.
Any way we took him to vet, vet said that the calf might have "colic", maybe why he was at the sale.
Calf managed to live, Until a freind talked me into castrating him.We cut him late in the evening, when I went to check on him in the morning, his guts had run out of his scrotum, and he was dead!!
I guess what I'm trying to say ( in a very long way) is don't castrate him, ya might be safe with bands.
I've raised "bottle calves" for 12 years, and in my experience, the pot bellied calves where calves that were not getting enough protein (ie: milk replacer) and were making up for that eating hay and drinking water.
I've always raised my bottle calves and given them as much milk replacer as they would eat. Makes awesome calves, but is not cost efficient. The last Simmental heifer I raised on a bottle from day one was 3rd at Ft. Worth last year.
I saw a pot belly bull calf sell this weekend. He was a 4w. The good stuff was bringing $1.30 and up. He sold for $.67. I started to buy him and throw him on corn for 120 days and make him into freezer beef, but I didn't want to take the chance.