Biting Biting on the back, big bald patch

[Pomegranate]

I adopted two pigs, a mother and daughter, a couple months ago (They're both around two years old). They adapted fine with my two sister pigs.

When I first brought them home, the mother pig had a sore patch on her back, it was the size of a 5pence coin. Her owner said the daughter pig had nipped it.

I kept my eye on it and while the patch of hair never grew back, it healed nicely.

Recently however, the bald patch is getting bigger. I've noticed it grow this past fortnight, and this past weekend, I have seen the daughter pig nip her on the back several times. She ends up with teeny dots of blood, she just kicks her away, but the patch is now a lot bigger, and I fear it will grow. It doesn't seem to bother her, the bites heal okay, but I'm concerned as to why the daughter pig keeps doing it. I don't think it's dominance fighting, the mom pig is really placid. I see the nipping happen when I go to feed them.

I've not had this behaviour in any pigs I've owned before, and I'm worried she'll start it on my other two. Any advice? Thanks!

Just to add: When I put the pigs in their box when I hoover their cage, I've seen the daughter pig nuzzling the other two pigs in the neck. They seem annoyed by it, I think she's grooming them but they don't like it. There's no bites or bald patches on them though, thankfully.

 

[Soecara]

Could you take a picture of the bald patch so we can get a better idea of its location, size, and appearance?

 

[Pomegranate]

Sorry it took a while, but here is a picture, thanks.

 

[bpatters]

Probably mites, maybe a fungus. I'd treat with ivermectin first, then an antifungal if it doesn't get better.

Here's the easiest thing to use, and the delivery is pretty quick: https://www.amazon.com/Ivermectin-Pour-On-For-Cattle/dp/B00JAL3AAW/ref=sr_1_6. If you get it, post back here and we'll point you to the dosage.