I agree with getting the vet - or take him there as he's already in the trailer. I would also have given him a long acting antibiotic straight away. If he had lain for a while he could already be getting pneumonia (laboured breathing) and the antiBs would help that.
He could well have a brain injury, in which case he will, as kanisha says, need a specific anti-inflammatory, but may die anyway. Until you can get him to the vet, either prop him up with bales, or if that doesn't work stand him every hour until he has burped and hopefully pee'd too. Has he had a drink of water? - he will need that especially as he has obviously been run down by the other males. Sounds like you need a fencing check too.
Good luck with him - a nasty shock to you both