If you look at the picture closely you can tell it is a witch probably cursed the cow making it a hermaphrodite so that the milk would be spoiled if someone tried to milk the cow and the spoiled milk would make all the other milk spoiled. Kinda a mean witch but I guess it was her own cow so it does not matter.
I am guessing that is a tier 3 witch skill so watch out popham the end is nigh.