US billionaire Steven Cohen has been forced to send his pet pig to an animal rescue facility after it became too fat.

The pig, named Romeo, had been a member of the hedge fund manager's family since he was a piglet and even had his own room in their 30-room Connecticut mansion, the New York Post reports.

However, after the pampered pet's weight swelled to almost 70 kilos and his placid demeanour changed, the Cohens took the advice of Romeo's vet and sent him to a vegan animal rescue facility so he could be with other pigs.

"Their pet pig was like a member of the Cohen family," the newspaper quoted an unnamed source close to the family as saying.

"Romeo had a room in their house. He was treated like the king of the house, but he got too big, and was sent to a sanctuary in Florida. They even threw a leaving dinner for him."

Romeo, who was first bought by Mr Cohen as a pet for his seven children, is reportedly the size of a German Shepherd and possessed of a more than healthy appetite.