Wound on pastern

["Lysane Cree" <cree_l@LSA.Lan.McGill.CA>]

I brought my horse Buck in from the field this weekend and I 
noticed a black patch of something on one of his hind legs. It 
looked just like dirt so while I was grooming him I tried to "brush it 
off" But what looked like dirt (probably was some dirt and junk in 
there) was dried up blood and the scab that had formed lifted right 
off. It is a cut of about 1 inch long, 1/4 to 1/2 inch deep. It bled for a 
minute or two and I cleaned it well and wrapped it. Since it was not 
hurting him, the bleeding had stopped completely  and there was 
no heat, etc. I went out for about a 1 1/2 hour easy ride in the 
afternoon (mostly walking, a little trotting). No problem so far. I left 
the bandage on until the next morning and then took it off  (it got all 
wet, soggy, and  muddy).  I have put some medicated spray on 
it(Blu-kote). That afternoon when I brought him in he was a little off 
and when I put some more spray on he pulled his leg away real 
quick. There is still no heat, but it is somewhat sore. I am worried 
that it is going to get infected. Anything else I can do? When I'm 
not around (during the day that means all day and into the evening 
sometimes) he is out in a large field with two other horses and I 
don't know about leaving bandage on him when he's out in the field, 
rolling around in the dirt and getting full of burrs. I'm scared that dirt 
and other gunk would just end up in between the bandage and the 
cut and make things worse. Any ideas?
Thanks,
Lysane and Buck