[The Might]

Still I think that makes sense

Firstly, it makes sense that similar creatures would be used as beasts of burden, because we see similar ones being used in our world
Secondly, we know cattle existed in the East. For example the Kine of Araw, the oxen that lived on the lands around the Sea of Rhun, and that were said to be descendants of the cattle of Orome.
So perhaps the cattle further east were much, much larger in size...could be a possibility.