The best thing worked for me is rat proof feeders. I bought two treadle feeders "I had to reinforce their closing mechanism with springs to make them more rat proof".
Other feeders you can try is grandpa feeder. wright feeder or trigger happy chicken feeder
"I live in Ireland".
I have wright feeder but recently it rained horizontal "the rain is carried by the wind horizontal" so it got some moisture and it needs to be "unclogged" I didn't do it because the hens are happy enough with the treadle feeders which are sheltered from rain.
The video below is for trigger happy chicken feeder and it is from their website so it is not neutral opinion
I bought two trigger happy chicken feeder, they are very simple design merely a small cross. I haven't installed them yet but I am planning to try them if I get broody hens.
Regarding rat poison, I use rat poison, but if you have it in well protected place you don't need to worry about chicken poisoned, and my neighbors use rat poison anyway "they have horses and cattles"
If you can show the authorities that you are using rat proof feeders then you are in a better position to defend yourself.
The other thing you can do is: whenever you see a hole put a water hose in it and let it run. rats hate that.
No matter what you do, if rats can get food they will keep coming
Go to
ebay and search for:
Rat Proof Chicken Feeder, you will get something