Can coat change cause rearing in horses?

Is she shedding her winter coat? Some horses can become a little sore or extra sensitive in the skin during a coat change. That could be one reason she is rearing, but because this is a new and unexplained behaviour, the best thing is to call the vet out to check the horse over, so that she is not in pain.

What matters for growing the new coat, once the horse has lost the winter one, is that she takes in enough protein. B vitamins have no effect on the coat, either when it is shed or when it grows in.