If you have horses and snow, you will sometimes be in for a shock as you walk out to check your horses and notice red or orange coloration in areas where the horse has urinated in the snow. This coloration is likely to be a surprise to people who are not used to being in snow. Needless to say, it can cause concern for horse owners.  Fortunately, in most cases this is not a disease process. The red spots you see are a result of your horse’s urine reacting with the cold snow.  Proteins in the urine called pyrocatechines oxidize in low temperatures, and this produces the red to orange colors noted in the snow.  So, if you see red or orange coloration in the area your horse urinated in the snow, do not be too concerned. 

However, there are some diseases that could cause real blood to be visible in the urine, so you want to make sure there isn’t any. The easiest method is to collect urine with a large clean cup duct tapped to a stick.  Although this is time consuming, it is necessary to rule out a problem. If the urine is normally yellow with no red or orange coloration, the horse is likely normal.  However, if the urine you catch is discolored, or if you see blood clots on the ground in the area the horse has urinated, call your vet. Horses can develop urinary tract infections that can cause bleeding, and they can also develop uroliths or stones in the bladder that can cause bleeding.  Additionally, they can also have a tear in their urethra or tumors in the bladder that would cause it. Some horses can bleed from the kidneys. 

So, it is likely normal if your horse urinates and you see red or orange in the snow.  However, catch some urine to be on the safe side and call your vet if it doesn’t look normal.