Had the exact same problem, you need to make sure the cat can't climb your fence and must be setup properly for an electric fence to work. I lost 15 to a bobcat until I set up my run like below. I used 6 ft deer netting, with many strands of wire. they can't climb the fence. bury some if the netting so they can't get under it, and make sure the fence has a good charger. Never lost another hen, and it been 7 months and I know they are around, cuz I see them. the deer netting is hard to see in picture which is good too, keeps hens in and everything out. good luck.