Join Date: Apr 2008
Location: Gallant, Alabama
That looks like a bad saddle fit.
My own mare has spots on both sides of her withers, worse than that, from an ill saddle fit from me using a synthetic saddle on her during her pregnancy. The saddle stretched out and gave her nerve damage, thus the white hairs.
I'd check your saddle-fit, just to be on the safe side.
Horseshoe Loop Farm: Home of Gypsie (22 y/o TWH mare), Dakota (10 y/o TWH gelding), Codie (18 y/o Walkaloosa gelding) & Harlow (9 y/o APHA mare)