Originally Posted by loosie
... As it's only a recent thing, it could be that she's in season, or it could be due to her being cooped up a lot more than usual.
... Keeping horses cooped up for long periods(let alone 24/7) is not good for them, physically or mentally. Of course, sometimes it's unavoidable, but the weather would have to be absolutely horrendous for it to be a reason for me to keep a horse locked up.
I agree and have found this especially true with mares. Our four mares are out 24x7 with a large shelter. They only use the shelter in the summer to escape the flies or in the winter when it's cold, windy, and raining (around freezing). If the winter weather is such that they decide to spend most of the day/night in the shelter, they are like kids with 'cabin fever' and do get very cranky with each other.