I just got a Great Pyr puppy for my fox problem, she is only 10 wks. old and since she was raised with goats and I have goats, she stays right in my goat/chicken pen.
Some things to consider with a Great Pyr:
They eat alot.
They make big piles.
You have to resist the temptation of cuddling them too much.
(if you do they will want to be at the house with you and not with the flock or herd, where they belong)
They might chase chickens for awhile and may even kill a few.
Did I say that they eat alot?
My pup was just wanting a playmate and since the goats weren't really filling that need, she found out that if she ran towards a chicken that it would run, so while she wasn't really trying to catch them, she was spending alot of time in pursuit.
My big, aggressive rooster was running from her too, so I didn't know what to do but yell are her. Finally the roo got tired of the game and flogged her good, she hasn't chased a chicken since and I hope she won't start back up again.