My mother used to feed milk ( it was left over milk from getting pig food) she would mix it into their feed or pellets, mash bread etc. They loved it and sometimes she would add youghurt, they loved that as well. however they seemed to keep getting sinus infections ( in the Bantams mainly) and so I would make up their feed without the milk. it was also bad when they put their entire faces in it as it clung to their feathers and started to smell really bad. I doubt your chickens will drink it if you leave out a dish, they might try it but I doubt they will lap it up like a cat or dog. you could try mixing a little dilutely into their food and see. Personally I just give mine some cheese ( grated or soft) because I know they can eat it and not get it everywhere, It also smells better and doesn't clog up their sinuses