I lived next door to a dairy for 7 years and raised two cattle myself from mother's milk to full adulthood. If you've never raised a cow I could say you know very little, but I won't be that rude.Farmers actually cut their fields and store grass in winter. Additional food has absolutely nothing to do with winter which tells me you are generalizing about stuff you seem to know very little about.
Giving them summer grass all depends on the season, whether the grass grew well, or whether there was a drought. It's not always possible to feed only on hay from the summer. In the UK we were feeding them hay over the summer, because all the grass was eaten, brown and crusty from the very hot weather. Which means there is less hay to give them this winter.
In addition, you keep answering things from your own point of view, while making sweeping global claims. The simple fact is, most people can't avoid eating meat from Brazil, or avoid meat that has been reared on imported fodder, often grown at the cost of the environment. Most people aren't eating meat that was raised locally, most have no idea where the meat came from.
We're either talking ONLY about you, or we're talking about the over consumption of meat globally and the damage it's doing to the environment.