HELPP sick guinea pig!

Question
hello, my guinea pig gave birth to guinea pigs 7 weeks ago, im keeping all 3 guinea pigs as they r all boys and have a big cage. BUT one of the guinea pigs 'Dave' is the smallest out of the 3 not ALOT smaller but deffinitly smaller. over the past 2-3 days dave's back legs and bottom half have been very lazy and all he wants to do is lie on his side on sit down , he used to be quite active and now is very calm and doesnt move alot at all. if i put him by him self say on the floor he will run a little bit but the back legs seem to hop a bit and if touched he lets out a bit of a sqweek, they both move so are not broken! i have put him by him self as when pushed over by the other bigger guinea pigs he has difficulty getting back on to all 4 feet. he is eating hay and some dry food as normall but havent seen him drink with out me using a baby guinea pig bottle! pleaase could u tell me what u think he has and if he will be ok. he is breathing as normall so i dont think it was essentail for a vet visit. do guinea pigs normally sit down alot and lie on their sides??
THANK YOU!

Answer
He most likely has a birth defect, or more than likely one of his spinal vertebres is out of place. It is not normal for guinea pigs to ever lay on their back or sit down, so he will need to see a vet immediately. Spinal injuries are very serious and can cause death eventually. If he does have a birth defect then nothing can most likely be done, so he will have to be placed in a different cage and taken special care of or be put to sleep. He will need to see a vet though, if a disk is just out of place then it can be put back into place by a vet, but permenant damage might already be done.
Brittany