I've never seen one on dark feet before. My two pink-footed piggies both had foot spurs, my dark-footed piggy never has. Very interesting! As others have said, it's a foot spur and won't hurt your pig. Some people do cut them back in case they catch on something and tear, but quite honestly, my pigs are so phobic about getting their nails cut that I was more afraid of hurting them while trimming the spur than having them catch it on something! My vet does file them down whenever a pig has anesthesia, so I can vouch that they will grow back. My pig, Sundae, has been put under several times for dental and abscess issues, and although she comes home with nice, soft feet, the spurs grow right back again.