"...She was laid off in late August and when I
brought her home in October she ..."
As you have already had answered by others, the
length of time white persists depends on the severity of damage. Before we
got OF saddles we had some that went away, and some that were
permanent.
Horse's hair does not grow the same speed all
year. After you do the damage, you have to wait for the hair to grow to
start seeing it. Hair damaged in late spring will not be growing until
late summer, so you will see it then. Your timing is such that it could
have been anytime since spring.
Ed
Ed & Wendy Hauser 2994 Mittower
Road Victor, MT 59875