I have an 7-8 month old bronze tom. He is about 45-50 lbs. Found him laying in the coop the other morning with his head stretched out on the ground. He wouldn't get up. I brought him inside because it was very cold out. He is fine when he is sitting down. He eats and drinks and breathes normally. If he tries to stand up and walk around he stumbles and starts doing this open mouthed breathing where he is almost gasping for air. He can't really walk...but he's always had problems walking since he is so large. His eyes and nose are clear, no discharge. I can't quite figure out what is going on...not sure if he is sick, in pain, or dying. Most of the time when he is sitting he seems just fine. Not sure whether to give him antibiotics or not. He's staying in my bedroom where it is warm and dry since I live in the mountains of Colorado and it is below freezing outside with over a foot of snow. He is a pet, not planning on eating him. Any ideas what this behavior could be? Thank you!