COLUMBIA, Mo. (AP) — "You want to get a new foot? Want to get a new foot?" cooed Kendra Earl Warlow as she bent over and petted Tucker, her five-year-old Australian shepherd.

Tucker bounced energetically around a basement lab in Noyes Hall, introducing himself to each and every person in the room. Born without several bones in his hind right foot, Tucker has spent his life hopping on three legs.

Warlow picked up Tucker when he was only eight months old and has stuck close to him ever since.

"He was the last one left in the litter. Nobody wanted him because of his foot," she said. "Nothing stop...