In my experience, the dairy farms that fatten their bull calves have arable as well, othersise they go to specialist rearers. The bulls are kept entire, fed cereals, kept inside and slaughtered at about 14 months ie an intensive system. Because they are entire, you need pretty good housing and handling facilities as they get big and boisterous very quickly.
The beef, apparently, is good but tends not to be in the right places for prime cuts.
This, to me, is another example of how the dairy industry shot itself in the foot by going to intensive milk production. Now they are reliant on the milk price - and Godknows the supermarkets arescrewing them on that - and the price of grain, because these high yielders need so much of it to stay alive. And they don't even have the cross- beef breed heifers and bullocks, and pure dairy beef bullocks to sell as another income stream. The fertility is so low in these cows that they all have to go to the Holstein to breed their own replacements. Sad.