Barn cats do a great service and I think 2 or so is an excellent idea HOWEVER.... kindness /animal husbandry should rule here and ALL barn cats (no if ands or buts) need spayed/neutered asap (usually 2 lbs) Anyone that would tell you differently hasn't dealt with the horrors of cat overpopulations or they just don't CARE. As far as cats bothering chickens its a rare cat that would (although it has happened its just a rarity) and you would, hopefully, follow common sense and protect any youngsters until they are full size. Although I have never ever had any of my s/n barn cats bother youngster fowl I have generally had a Mama bird with the youngsters and that can help immensly. Again- no if ands or buts on the spay/neuter thing. You can find many places that will adopt out feral/semi feral/tame but have inside issues spayed/neutered/vetted cats.