I have been shooting rats for the last four years or so and have tried just about every combination you can think of some of my better baits are, yoghurt stored in a used washing up liquid bottle so you can easily put it exactly where you want it, some of the thicker yoghurts I mix with a drop of sunflower oil and use a hand blender to mix.for fussy rats mix a small amount of gravy granules in with anything from yoghurt, believe me it works.
Nothing goes to waste in my house if it can go in the blender it gets used, for a "ToP Tip" go to your local Tescos or Asdas and look in the reduced s