Protecting the Chickens

I originally intended this not as a post, but as a reply to a comment to my last post (by 'anonymous'). Anonymous stated various critters as a concern to having chickens. This is a very real concern!! Friends of ours have lost several chickens to racoons. They would attack when the chickens stretched their heads out the wire to grab grub. Our friends would find headless bodies in the morning.
We've lost one bird by accident. We moved the tractor at night, after the birds were already asleep. It is hard to see how many you've woken up when they're mostly all dark colored and it is dark out. We think we rolled the tractor over one poor bird and killed it.
Our newest "threat" is Jomo. Technically, Jomo Lager (as Shannon won't hesitate to tell you). Jomo is our 6 month old American Bulldog & Bandogge Mastiff mix. A Bandogge Mastiff is, for those of you wondering, a breed created by mixing Mastiffs and Pitbulls, mainly. He's truly a big baby though. At his last vet visit, just last Thursday, he weighed 56lbs!

So, the question is: why is such a big baby a big threat to our little Biddies?? Well, because he is a curious little pup!!
This evening I went out to check and see if we had anymore eggs - we didn't. Instead I find Jomo standing against the tractor's wire "walls." This isn't anything too new, he likes checking the gals out and is jealous of food they get. I yelled at him & instead of getting down the little turkey CLIMBED UP & OVER the tractor!!!
So, new task: fix the tractor. We already have "build a nest box on the tractor" on the list for next weekend. Now we also have "make tractor Jomo-proof" on the list. I'm not really certain how this will go. If anyone has any ideas how to make a chicken-wire, chicken tractor puppy proof, I'd love to hear it! Jomo should turn out to be a good 100 pounds or more, so this is a big issue for us! Ideas?