We hatched 7 Cream Legbar cockerels in May and they have been doing really well and are already integrated with the rest of the flock (a gaggle of some 15 mongrel hens and cockerels we inherited from previous owners of our house). Out of the four male Lebars, one is very large, two medium, and one quite a bit smaller in comparison - although still a good size for a cockerel of his age I think, and quite plump. About 3 days ago I noticed a small limp in the small one, then the day after a more severe one - it seemed there was pain in his left leg. We've kept him indoors in a box with straw since, and he's not making any effort to stand up. He's eating well and seems perky, but if anything he seems even less inclined to stand up than yesterday. We put him outside to get some sun and another hen rushed up to attack him but even then he couldn't really get up. He's eating pretty well still and doesn't seem to be distressed. I've examined his legs and feet and just can't find anything in them. His poop seems fine too - green and white and not too liquid. I'd really like to help him but I'm not sure what's wrong. I also really want to know if there's a disease entering the flock as soon as possible. We haven't brought in any birds and live very remotely so it would be very hard for diseases to get in, and nobody else has shown any signs. I'm wondering if he has a nutritional deficiency (he's fed on maize, wheat, chicken food from the store and bread soaked in water). I wanted to do the test where you give them a little bit of aspirin and if it's an injury that should get them back walking (and then just rest him again) but unfortunately I can't find any aspirin in the house - would ibuprofen or paracetemol work? The only other factor I can possibly think of is that we had a major rat problem recently (thanks to some over-zealous house-sitters who spread wheat all over the place for 3 weeks) and had to poison them because nothing else was working (they were chewing through plastic barrels to get to the food, it was that bad, and crawling through the windows of the house). It would have been impossible for the chickens to get any of the poison, but several of the rats died in the run and were partially eaten before we found them. The poison we used contained bromadiolone. Could this have caused the weakening and then loss of the use of his legs?