Sounds like a fairly decent population. Keep smoking them, keep traps out. Mk4's may prove more helpful. Also, poison may help. Sometimes its not always a problem of killing them, but stopping them living. By this i mean you may need to tidy up. All living things need 3 things. Shelter, food and water. Remove two of these and you make the rats either die or move on. Get you chicken feeders/drinkers off the floor. Remove any place they may want to live, such as old feed bags, hay bales etc. Any spilled grain or wheat, tidy it up. Worse case scenario, ask a professional opinion. These are all th