yellow snow...?

["Cameron Wood" <wood.cameron@acd.net>]

Hi group,
     I wondered if any of you (especially in snowy areas) have had any
experience with reddish-colored urine in the pasture. Lately I've been
seeing "reddish-orange" patches in the snow along with the more normal
yellow pee.   Anybody have a clue what's causing this, and if it's
something I should be concerned about?  All my horses seem to be fine,
eating & drinking normally & active. It's been very cold here, in the
single digits with minus 15F windchills most days and colder at night.  My
guys are on 24hr turnout (no barn, yet :-((  )  with a shelter large enough
for all of them to share (which they do). They are all in good flesh right
now & getting  extra timothy/alfalfa to help keep them warm.  I have not
stood out in the cold long enough to watch them all urinate to see which
horse is staining the snow orange, or even if the fresh urine is this color
(would it turn orange later?)
  I have asked my vet about this, she doesn't have an answer.  My neighbor
is also seeing the same thing in her horse's pasture, and her horses seem
fine too.   I am concerned that it's because of the severe weather.... that
maybe one of my horses is burning muscle to stay warm and the reddish color
is myoglobin in the urine....?  I have a hard keeper that isn't very cold
tolerant and always needs extra care in the winter.  Any ideas? Thanks for
your input.....

Shannon LVT
Laingsburg, Michigan