what size rats are they,,,,,,, nevermind,, i dont know how your killing them now,, but gassing them is way better than however your doing it . you dont have to wack them on the head, or anything like that,, just put them in and be done. 10 gal aquarium, small co2 tank, plexiglass top to fit the top of the aquarium, and some plastic hose and your good to go. gassing is about the easiest way for the rat,,,, and you.
spooky