LaSombra, My moat is only 2 feet wide in the part that goes around the garden. The part where it's more of a 'run,' varies from maybe 5 feet to 9 feet. The paths in the garden are all 3 feet.
NCricky, I have no experience, since my chickies are all still in the brooder inside, but I have done extensive reading on what chickens, ducks, and geese will and will not eat. From what I can tell, it really depends on your poultry, as some people say a chicken will decimate a garden and others have better luck. No one appears to have good luck when things are just starting to come up. It appears chickens eat some things and not others.
Same with ducks and geese. One person said ducks ate all her hostas and another said her ducks leave her hostas alone.
So I think it's a trial and error sort of thing. I know I wouldn't put a chicken into my garden without being there to see what goes on!
I know lots of people will put the chickens into the garden only during the winter and nongardening months and use the chickens to till everything up and it's nice and ready-to-go come spring planting. That doesn't work for me because I have about killed myself laying out those mounded beds and don't want them mucking that up for me.