Daisy, my neighbor's chickens a couple of years ago decided they liked to roam over to my barn. They would spend the day crapping on everything and laying eggs in the hay, which would end up either rolling down between the wall and bale stack or be buried enough in the hay that they would end up smashed on the hay and I lost half a bale to the mess. My neighbors finally stopped allowing them to free roam, but one chicken refused to go back home and she ended up becoming kind of a pet. I kept her for about two or three months, but in that time, she learned to roost on top of Tipperary's stall wall, where she would vent into his water buckets. Or down the wall, In the aisle , where I or others would track it into the tack room or my truck.
I found a home for the chicken with a friend who keeps chickens. It took me days to find and clean up the mess they left behind. I would do everything I could to not have my horse around chickens. I know other animals shed salmonella but chicken manure is not easy to find in hay, feed. You can't keep water buckets clean 24/7 with chickens roaming, flying and roosting. Just my opinion but based on a years worth of experience.
Dawn Wagstaff and Tipperary
Saline, MI 2003