Not that I know much about horses, but I took a western horseriding class as a kid and they taught me that horses do the same thing when you saddle them - expan

Not that I know much about horses, but I took a western horseriding class as a kid and they taught me that horses do the same thing when you saddle them - expand their bellies so you can't tighten the saddles too much. The instructor would give them a healthy slap in the ribcage to make them relax and then cinch it up.