Re hens - mine are that tame that they will sit down and let my dog sniff them. He's nuzzles them all over and then goes on his way. He has such a mothering instinct that he sneaks into the pen when I'm with a farrowing sow and even starts licking the piglets dry.
My local farmers two working dogs are always pottering around the farm with the hens, geese, and quail that he has without any bother too.
Surely if a dog is brought up and taught that it doesn't chase them from the start then it won't get into that habit from day one and become set in it's ways thinking that it's perfectly acceptable. Personally, I'd expect any working farm dog I have to be completely safe around all animals.