What IS this ?

Fly Cyst ? I have NO idea, never seen anything like it before. It's on my horse's back, right along his spine. It's been there for at least a month, and it looks like it's getting smaller. He's really underweight and he's gaining it back fast. The more weight he's gaining the more it's going away. When I first got him you could see the his back bone, that one was just 3 x the size of the other bone "bumps". There's also grey hairs growing out of them now that weren't there before. Suggestions?

My first guess would be a bot fly. Is it squishy or hard?

Then again, it could be some kind of bone spur or growth. My old guy Denny just developed a bony growth on his spine that would likely look like that if he was thinner.

Also like to add he's only 2 and he has never been ridden or had a saddle on.
And it's hard, it feels like a bone. A bone spur, maybe. But how does that happen? He's got white hairs sprouting, so that's a sign of some sort of trama, I believe.

Hm, I'm not really sure. With it sticking out that much, I would probably have a vet look at it before I thought about starting him under saddle.

Your right. Also, do you know what a fly cyst is? It's been brought up to me a few times, but i've never heard of it before. I've been told it's a fly bite that I guess .. turns into a cyst? But how does this happen and is it potentially that?

I don't really know what they are talking about with a fly cyst. The only thing I can think of is a bot fly larvae that maybe imbedded itself in the horse.

I couldn't find a pic or video of them but it is just like this only on a horse's spine.
Be warned, the vid is a bit graphic.

SO gross. I'll have to have the vet out to find out what it was. My first thought was it was a calcified bone chip or spur. It seems to be directly on the bone. If you look the rest of his back bone is showing too.

Putting money on bots over bone chip simply by playing the odds. What has your deworming protocol been?

Aug 1 Ivermectin 1 Botocide
Aug 1 - 30 Contunuex Feed thru daily
Sept 20 - Ivermectin

How can you tell if that's the case? And what do you do to get rid of it?

Also, he's got a millionnnn bot eggs all over his legs. I think I got them all and the next day there's more. SO that's very possible..