When my one piglet had a URI she got a tiny bit of diareah from her meds. She then got something between her little toes that looked like that. I thought it was poo then tried to remove it and was sure it wasn't. I soaked a towel in luke warm water and applied it to the "thing". Low and behold it finally started to break apart and it was poo! Now it hadn't been there long, maybe only a few hours. But it came off fairly easily with the warm water. Good luck!