RED SNOW: If you see red urine spots in the snow (or fresh shavings), don’t panic. Normal horse urine contains plant metabolites that oxidize to a reddish hue as it sits, known as pyrocatechines. This happens year round but is most noticeable on the white backdrop of snow.
If your horse’s urine is red during the evacuation process this is cause for concern, and your veterinarian should be contacted.