Thanks Much--I thought rain rot too--not normal shedding as in past--12 years old--very healthy except this. Im getting shedding blade and medicated shampoo this weekend. It will be 80 here in Sulphur Springs Tx this weekend.
Only white areas affected? Photosensitization.
Grazing pasture with white or red clover? Hay with clover in it? Most common cause I see here is Rhizoctonia spp. mold growing on clovers.