As you already have gnaw holes you definitely have a rat infestation .
Warfarin based baits put in tubes and pushed in with a bit of soft sponge to the middle in such as laid down 3 inch drain pipe 1 mtr long laid by walls and staked down to stop dogs getting the bait are about the only effective way you'll ever get rid of them .
I have made my bait stations by cutting a " V" out of a four foot tube and inserting a vertical tube about two feet long into the " V" and fuse gluing it in place to make an inverted letter " T" About a foot in from the two ends of the tube that lays on the ground I've slipped in & glued a bridge about 10 mm high to hold back any bait & to help stop birds hopping in for a feed.
Once a month I use a small torch to look down inside the top filler tube , if the bait has gone I'll add another cup full and replace the old clear plastic pop bottle cap on the cube . If after four months none of the bait has ben touched I take the trap up , empty it into a bucket and replenish the bait with some new stuff .
Even then you'll still need perimeter vermin control stations for as long as there is food available you'll be a rats first stop off .
They usually die deep down in their holes after a feed , if it is a succumbing doe suckling her young , her milk will snuff out the baby rats very quickly . If they are of a meat eating size they will eat her and also die from her ingested poison .
Should you notice any of your dogs being unwell if they have eaten the bait or a bait fed rat an injection of vitamin K puts them right .
In the unlikely event of you finding a dead rat collect it in a poly bag and burn it ASAP , don't bury it , put it on the muckheap or leave it on a shed roof for the flies as a bird of prey or carrion might take it .
One of the best brands if bait I've ever used was called DRATT though I don't think it is available to non registered pest controllers any more ..I had to sign the poisons register for it . You add by the cap full it to mixed bird seed in a cement mixer along with with cooking oil , dried milk and cocoa powder.
A more common bait is the Neosorexin baits usually available in 500 gram and 5 kg buckets ready mixed from any horsey place or agricultural merchant . Don't buy the sachets of it as the rats drag them away to take them back to their nests frequently leaving them on the surface if disturbed by an owl or human etc.