Emma's Hoof
About 3 weeks ago Emma came up lame.
She didn't want to walk around much, and was head-bobbing
lame at the walk on her right front.
The vet was out, used testers and said an abcess. He gave her
antibiotics and bute for a week.
I checked on her in another week, and noticed that a portion of her
hoof wall was completely separated from the hoof. I called my
farrier, and we scheduled for him to come out.
The following shows what he did.
Here's a link to a good description of White Line Disease.

First he cleaned out the area where the hoof wall wasn't attached to the foot. Before he cleaned it out, his pick went in about four inches into the space.

We agreed that to get air to the yucky white line stuff (fungus, I believe), the unattached hoof wall needed to be cut away.
Starting to cut away. It was dead, but cutting all that off made us a little nervous.
After the first section was cut off, we could still see a lot of bad, black stuff that needed to come out to help it heal.
This is as far up as we went. The farrier prodded as he continued up, to be sure everything was dead.
There's still a little black stuff showing, but hopefully as we treat it, that will all go away. If not, we will consider digging out more. I find it interesting to see how thick the hoof wall is this high up. The farrier said that in any healthy foot, there would have been a lot of blood in this area. Some suggestions were to cut away until it bled, but we didn't want to go that far.
Here's what it looks like on the ground. The first night I left it open to get air in. In the morning I had to clean out some dirt, so I'll probably follow the vet's suggestion of packing with cotton soaked in a bleach solution to try and kill the bad stuff and keep it cleaner.
One thing I read said that you can soak the foot without cutting the hoof away, and then see if it gets better. Then if it doesn't, go ahead and cut away. 
I think if this hadn't been so far up in the hoof wall, we'd have done that. With how high up this was, I don't think soaking would have reached the spots that needed healing without doing what we did. Also reading further, it seems air is very important to killing the fungus.
We checked her other front foot, and there was no separation at her white line on that side. We tend to think she got a piece of gravel between her wall and hoof and that could have started all this. We didn't trim the rest of the hoof or take off any sole or frog. The farrier felt she'd need all the support that she could get from the rest of the foot. With a nine inch foot, we didn't really consider shoes.
The farrier applied merthiolate to the affected area. We'll use this or bleach a couple of times a day to kill the fungus. Luckily she's very good about picking the foot up for us to work on it.
The farrier thinks this will take at least five months to grow back out. We're still not sure why she's lame, but we'll be watching carefully for abcesses and keep her on softer ground. We're looking into getting her a soaking boot, to let the foot soak maybe once a week.