In EU it's a mix: https://www.dairyherd.com/news/european-cows-eat-more-foreig... https://www.beefmagazine.com/americancowman/beef-and-busines...
In general different countries will "finish" their cattle with different grains. Only a few places have the right conditions to have their beef be grass-fed through its whole lifecycle.
Not ideal, but I think cows are pretty flexible when it comes to cheap calories.
Edit: yea def happens https://money.cnn.com/2012/10/10/news/economy/farmers-cows-c...