They are several things to consider in a situation like this,Do you live in a rurial area where it is safe to shoot a rifle?Will you be shooting during daylight hours or after dark?How far is your nearest neighbor? A 22 slug from a 22 long rifle will travel over one mile,How much experience do you have with a firearm?Shooting someones dog and sending it home bleeding from a bullet wound is not a good idea,It could lead to a civil court case and expensive fines for animal cruelty if you can not prove the animal is a danger to your chickens.I am not saying you can,t protect your property but shooting a pet can be serious,As far as one gun for all situations is a difficult choice,almost impossible,I would go for a 22 single shot rifle and either a 12 or 20 gauge shotgun,The newer model shotguns fire the 3 inch magnum shells that will take down any four legged critter in North America,also a single shot will make you a better shot and also you will not use as much ammo and have better control of the situation,Whatever you choose take someones advise that was posted,,get training and practice,,I am a hunter with 60 years+ experience with all kinds of wild game and predators,,Good luck with your choice,