I don't want to be critical but the combination of barb wire and T posts is a disaster waiting to happen. I have seen injuries where horses have been impaled on the T Posts. With the fact that they are so thin it is also very difficult to have them deep enough into the ground for them to be firm fencing to hold against a horse leaning on them or running into them. Add the barb wire into the mix and I cring at what could happen.
If nothing else make small slits into tennis balls and put the tennis balls onto the top of each T post-that will at least give something to deflect any soft tissue from the top of the post.
Best of luck with the horse=and please only take my suggestions about the fencing as a positive observation that needs to be carefully watched with any livestock enclosed with it.