The first thing that I noticed is that he was just really on edge.....normally he objects a little bit when I first start brushing him, but this time he was full on stepping away, baring his teeth and trying to bite me, and he even swung his butt towards me at one point. It was really only on his right side, but even on his left he was still just a little "off". So I ditched the brush and just started touching him, which illicited the same reaction, to me at that point meaning he was just in a bad mood. He was really unhappy when I was pushing on his gut, but there were good digestion sounds and he had three or so piles of poop in his stall. He also had a wet spot (on his right side) where he had obviously been reaching back and biting, but that was near his shoulder. He wouldn't let me touch his chest at all (I was fitting a new blanket) but everything was resolved when I took him out to the front of the barn and let him graze for a little bit. He let me touch him anywhere with no problems. I decided to try tying him in our arena, and although I didn't have any problems there either, he was also non-stop cribbing, which is unusual for him. Normally, he cribs once or twice and then just stands there or moves on.
So does anyone have some insight? I'm used to a sullen attitude, but this afternoon he was just hostile. According to his farrier, which I brought with me from his old house, he did go through an "adjustment period" where he was mean to the other horses and had to be separated, which is what is happening now. Is he really just being extra jerky and trying to test me, or could something be wrong?