Someone always pipes in with "chickens are lactose intolerant" but this is a human deduction. Soured milk or milk made into kefir, live culture yogurt, or buttermilk doesn't seem to bother them at all. Once it's soured, or turned into live culture kefir or yogurt, it no longer has that same lactose. Same with raw milk. They digest it fine. It's just fresh homogenized milk that causes a problem. And this is from science plus observation.
