Not 100% but a very large majority of their feed would be fresh grass or silage[1]. If you can't make a profit feeding them grass why are you raising cattle? The economic calculus changes a lot if animal feedstock is highly subsidised like soy or alfalfa in the US but for all its many, many flaws the EU's common agricultural policy is mostly about things people want to eat.
[1] Less confident about this for Australia but I still think that's true.