Your milk from that dairy could be pasturized but not homoginized, or not homoginized very well.
LOL I have no idea if it was legal when we used to go down the road and get milk straight from the tank... I know we didn't pay them in the barn, we stopped up at the house and got some coffee and had a chat, leaving some money there, in two nearly unrelated exchanges! *shifty eyes*
Neither I nor any of the rest of us neighbors got sick, it wasn't pasturized or homoginized, (though they owned a small pasurizer, it sat in the kitchen, kinda dusty and forlorn, technically, they weren't even supposed to drink it themselves, CALL CHILD WELFARE!!!) hehe... but one thing, WE didn't go in and get the milk ourselves, it took extra time and work for the farmer to do it, but he took care not to have too many extra hands in his tank. Kids could go visit his cows, most were pretty nice girls, but they weren't allowed near the business end or the tank to spread or catch germs.
His barn was clean and dry, and his girls were only in the feedlot for a couple hours while waiting to get milked, then it was straight out to a nice green pasture. He's out of business now, he couldn't afford to keep at it.
[edit] I've heard of chickens loving buttermilk which is actually the very runny liquid left after making BUTTER, not just milk with the cream skimmed off, which is indeed, skimmed milk