Yesterday while I was tacking Nina up, she tried to lay down. Several times, girth was not tighter than normal and she had been acting fine. I got the tack back off of her quick and turned her loose in the roundpen. My first thought was colic so I grabbed a stethoscope and listened for gut sounds, everything sounded fine. Turned loose she wandered around, rolled once, nibbled on weeds and acted perfectly normal.
It could have been
1. a gas bubble that made her stomach hurt just as I was tightening the girth
2. she was holding her breath
3. this is another trick she has learned to get out of being ridden
Tacked her back up and then she was wild, running and bucking.
But when I got on her I get the best ride so far, just walking. Happy, forward, big even strides, no resistance of any kind, ever. I was very pleased with her.