Have you had a look at why you have rats? You can lower the attraction of your place to vermin by measures such as storing all feedstuff in metal bins, making sure no poultry or other livestock feed gets left scattered for the rats, avoiding bird seed from wild bird feeders lying on the ground, scratching up rat runs. It won't deal with the problem you have now but will help.
When we had a huge sudden influx of rats some years ago, it was when a neighbouring farmer was storing his harvested grain in a large open-fronted barn. The rat population exploded, then all the grain was used, so all we lucky neighbours roundabout suddenly became hosts to the millions.
We shot them, poisoned them (using bait boxes), and bought a couple of terriers
. We made sure there was nothing for them to access for feed, or as little as possible, and after a couple of years numbers were back to 'normal'. Now we rarely see them.