Couple barn jobs I had recently. Cows actually started chewing through a 200 ft run of our wire in multiple places. my helper had gottin a little to far ahead of me.
I once drove about 200 miles each way to troubleshoot a telemetry RTU that had failed. Turned out a horse had switched it off scratching his backside on the RTU. I caught him doing it when I arrived. I offered to relocate the power switch to the inside of the enclosure, but the customer opted to build a fence around the unit.
And don't discount rabbits as cable-chewers. They love PVC for some reason!
I know that many plastics use plasticizers that are estrogen-mimicing. Maybe they also attract rodents with their smell. Rabbits will completely strip the outer sheaths from COAX or Heliax if it is low enough for them to reach it.
Use the attic to run your wires if possible. Calving pens and inside the robot milking parlours are some main focus points I’ve done. Also the outside petro tanks too. maybe a couple of good motorized zoom lens cameras inside, depending on how long your barn is.
I once worked with a guy who grew up on a dairy farm in an area with cold winters. He surprised me when he said the barn was warmer than you would think with all those warm-blooded cows in there.