Hey guys, I was wondering if anyone has seen this before and can tell me what it is? My horse develops white spots along his back and rump as his winter coat comes through, they go away again during summer months. There's nothing on the skin at all that I can see, it's just the hair growing through white. I've owned him six years and the first few years I had him I remember one or two spots coming up but as he's getting older (he's thirteen now) they seem to be multiplying each winter *#). Anyone know what might cause it? There's no issue with it at all I'm just really curious as to why my Standardbred turns wannabe-Appaloosa over winter .