Paralysed chicken

[racaille]

Hope someone out there is a chicken expert .....
One of mine has suddenly become 'paralysed'. She was absolutely fine when she came in to the run last night (they are free range during the day) but this morning I found her sitting down, unable to move her legs. She seems quite alert and has put herself in the shade somehow or other, but when I offered her a lettuce leaf and some soaked bread tonight she didn't seem interested.
She is home bred, 2/3 years old. It was a closed flock until about a month ago when I bought four hens from a friend who keeps about 60 (in good health) so I've no reason to suspect any disease such as Mareks or coccidiosis. Having said that, no one bothers to vaccinate chickens here. I might bung some cocc treatment in their water tomorrow anyway, but it's difficult as their water is free-running.
Again, calcium deficiency could be a culprit but unlikely give that they are free range and also get a layer's pellet.
She may well die overnight but I'm reluctant to cull her in case it's something simple. (Although chickens die so easily ...)
Any ideas?

[Blonde Donkey]

has she broke her legs? or is she just not able to use them
my dad found a duck with two broken legs and it lived for ages, plus if you left it somewhere and told it to stay it did

[kateflashy]

our rooster went like that after a snake bit him gave anti venom but was too late he died the next day i dunno if you have the same black vipers in your area but apparently they do bite alot of chickens

[jack]

its been a long time we had alot when i was a lot younger but it tends to just happen and i hate to say it but they dont tent to get better some times its just kinder to well you know