We have movable runs that have kept rats to a minimum in the past, but now within 2 days of moving there are always heaps of them.
Are you collecting your feed at night? Honestly even though I collected feeders EVERY night.. I found there was enough "shrapnel" left around from the birds, they still came looking.. but every effort matters.
Pics of your runs? If a rat can get in so can many other predators. Rats have even been caught eating a live chicken and are considered predators themselves aside from the whole parasite and disease vector, or feed cost incursion stuff. Are they coming through ground tunnels, digging under at the side walls, or how are they coming in?? Is it mostly night or also daytime?
Red pepper flakes or crushed red pepper added to the feed.. poultry don't sense the capsaicin heat but rodents can't stand it. Short term just long enough to let them know this isn't their preferred buffet anymore.
I have used wire bottom in non moving coops with plenty of shavings or soil on top.
half inch hardware cloth is effective, chicken wire is not. I wouldn't consider it an ideal solution for moving tractors.. though suspect the birds would adjust and adapt soon enough (quickly learning their scratching limits so they don't hurt themselves).. Presuming it's in full contact with the ground so they aren't actively standing on it with full body weight being supported by wire alone. (Might make dragging to a new location a bit more challenging if it snags on stuff) Provide a dirt bath in a container if going that route. While it may not generally be ideal.. sometimes we do what we need to in order to best manage our flocks. Things do change throughout the years including wildlife load.. which rats are part of.
Hmm.. I wonder if one of those fake owls with turning head would help you? None of my animals are fooled by my neighbors and rats are anything but stupid.. but worth mentioning.
I also employ barn cats.. which comes with other pluses and minuses. Car food ain't cheap.
Trapping isn't effective.. you get a few here and there but never truly touch the population. Some folks in my area (Craigslist farm and garden section) are bringing out dog teams with astounding results, though it's quite the ugly scene. (Jack Russel or rat terrier and the like)
I would say skip the whole rats don't fart thing trying to kill them with baking soda mixed into something tasty that wouldn't in theory effect any animal that does pass gas.
Despite facing my share of rodent battles, they can be quite challenging and I'm certainly no expert. Still I hope my words will give you some things to consider and also that you will get more feedback.
Consider adding your location to your profile as it may help folks make their best suggestions possible.. regarding what resources might be available, certain predator suggestions, and weather indicators etc.
