The Field Marshall, a bull owned by Arther Duckett, 78, was weighed on a scale used to determine the weight of trucks during the "Guess the Weight" contest -- which raised money for a new oncology unit at Musgrove Park Hospital in the town of Taunton' -- and was found to have gained 500 pounds since last weighed in 2007, the Daily Mail reported Monday.

Duckett said the6-year-old Charloais bull is the heaviest in Britain.

"The Field Marshall is a monster specimen, no doubt," Duckett said. "And unless anyone else comes forward, he is also the heaviest bull in the world."

The owner said his bull will likely continue to grow for some time.

"He's still getting bigger. Field Marshall is still just a teenager really -- he's got a lot of growth left in him yet," he said.