They aren't grown to adulthood usually. Some are slaughtered right away to make Bob veal, some are formula fed to make white veal, some are gain fed to make red veal, some are intermediate or pink veal.

https://en.m.wikipedia.org/wiki/Veal

The milk industry and the main beef industry are mostly kept separate and are different breeds. Though, old cow are sold as cheap beef once they are done.