Regarding locking the shed: It's an old iron cladded shed with more holes than swiss cheese so locking it isn't the point. (infact its always locked).
My dogs don't actually eat the rats! They just gently crush them and throw them in the air like toys. After a while the rats are dead though. It's the thrill of the chase to them I think!
I have been told it would be unlikely that they would get sick if this is the case.
Anyone know how quick a rat will take to die after eating the stuff?