This is a "hairy heel wart", one of the most costly health problems in modern dairy cows. The "wart" grows rapidly and causes severe pain. She becomes so sore that she will stop eating and drinking. Milk production drops. At this stage the illness is also highly contagious.
...Four Days Later!
The same wart four days after application of HEALMAX® has stopped oozing, formed a tough waterproof scab, and the animal is free from pain. She is no longer lame and her appetite has returned. The wart is gone.