Most of it is just a giant outdoor meat factory, though. Same for Ireland. Meat, fortunately, is unnecessary and very inefficient.
There is a lot of arable land in England itself that can be used, (and, currently used for meat production); however this is not true for many parts of wales and most of Scotland. (which combined make up a about 100,000 sqkm vs Englands 130,000 sqkm)
Harry Metcalfe has a good video[0] about it - he keeps cows on the fields that are just too steep and too rocky to grow anything else - but it doesn't bother animals. Same applies to sheep. I imagine animals like chickens will have different considerations, because farm buildings do take land that can be used for something else.