rats!

[son of eddy]

If possible try and raise your poultry house a couple of feet off the ground and have it so as there is an open space unerneath the hut visible from all sides. 
This will discourage the rats from burrowing under the hut as it makes them vunerable to attack.
Second thing, rat poison, there is always the possibility of children, cats, dogs picking up the poison, try putting it into a lockable box.
Something like this -

Generally these boxes have rods in that you scewer the poison onto.  USE DISPOSABLE GLOVES WHEN YOU DO IT AND DON'T ALLOW THE POISON OR OUTERSURFACE OF GLOVES CONTACT WITH YOUR SKIN. 
Also about once a year change the poison product

[amberlove]

You should keep your food away in a sealed box (I use a bench which you can lift up the seat which seems to be working). Not long ago I had rats but I recomend to buy a rat trap but take it away when you bring out your animals. This should work as rats tend to be out at night. Have you tried a trap-door for extra protection? They are quite easy to make and keeps your animals safe and locked in so there won't be any unwanted guests. I hope that this will help.