our cats don't bother the chickens, they never have.
most of the chook, 'specially the hens can get nasty with the cats,
I came out the other day to find that the big Light brahma had one of the cats PINNED to the ground pecking at his head!, the cat was hssing and spitting, and clawing, trying to get up, what was it all about?, the CATS food bowl, MIL didn't pick up the feed bowl for the cats, and the chickens think it's theirs. when you put together the over all size of the chicks, compared to the cats, we have a several smaller cats, and the chickens tower them.
that and the amount of damage that a chicken can do with beak and claws,.
well, the Brahma got kicked across the field before she killed the cat.
ANY kitten or young cat is going to test it's boundries, what would happen if when the cat and chicks were older the young cat killed one after all your "training"?
if you've got mice, by all means, get a cat to control them, or get some muscovies.
but don't expect to "train" a...in a sense, a WILD animal.
especially a cat, who will always view a young chick as either, 1. something to play with, or 2 food.
ETA: there really is NO way to keep a cat from wondering, even altered cats will wonder and set up a territory, we have 4 intact toms, and they're all lazy lumps, they stick around the house unless theres a girlie out there beckoning them with her "spring and summer needs".