Ushi Ushi no Mi, Model: Bison

The Ushi Ushi no Mi, Model: Bison, also known as the Ushi Ushi Fruit, Model: Bison, is a Zoan type Devil Fruit that allows a person to transform into a bison hybrid and a full bison. "Ushi" means cow and the fruit is one of the many Ushi Ushi Fruit models. In the 4kids dub, it is simply called the Ox Ox Fruit. It was eaten by Dalton.

Translation and Dub Issues
In the 4kids dub of the anime, the fruit's name was changed to changed to Ox Ox Fruit in order to convey to an english audience. While this is technically correct due to fact that the japanese word "Ushi" can mean either cow or ox, due to the lack of any words suggesting otherwise, the name in the 4kids dub technically implies that Dalton turns into an ox instead of a bison. While both the words, ox and bison, are sometimes interchangable, they technically refer to two different breeds of bovine.