You will need a source of straw to bed them on overwinter , and you'll be surprised how much 3 beasts eating silage and having outside access , so getting wet will use . Somewhere to keep the straw dry , not vital but preferable . will you be feeding in a ring or half a ring on the concrete pad ? Do you have a loader to handle the silage ? or maybe a hay knife to cut it in slices . Some way to keep the outside pad clean ?