We have a Silver Appleyard of unknown age (less than year, more than 6 months) that seemed to be limping a bit yesterday, but wouldn't let us catch her, and later in the day we couldn't pick her out from the rest of the group, so we thought she was doing better. Today, she has spent the whole day in one corner of the pen, and is breathing heavily. It was easy to catch her, as she seems to have extremely limited mobility on her right side. The leg itself doesn't seem injured (doesn't appear broken, no swelling), but it's clear she can't support much weight on it. Any thoughts on what might be wrong, and what we can do for her?