If they've plenty of straw in the arc (providing it's not damp straw) I wouldn't have thought it would be a chill - ours coped with -20 last year without any problem - they're pretty hardy

But you don't say what age or breed so it could be a young, not too hairy breed which might be more susceptible to the cold ?
Temperature being raised suggests an infection of some sort - are any of the others showing signs ? Do they have good ventilation in their arc ? It
could be pneumonia, so some antibiotics would be in order.
Does the new field border any sheep has the land been used for sheep ? It
could be clostridium, but it also might not be

If one of mine goes off food and has a temperature I tend to err on the side of caution and (after talking to the vet) I usually give penicillin or other anti-biotic. I don't mean to be rude about your neighbour - but unless he's kept pigs before he could be talking rubbish (from experience here

My dad's a beef farmer - but knows diddly squat about pigs

)
There are lots of things it
could be but I'd suggest giving your vet a phone (they don't usually charge for advice on the phone) and talk it through with them..........just to be on the safe side. (but bear in mind the withdrawal times for medications and slaughter)
HTH
Karen
