Poor guy. Watching those videos he reminds me of a more severe version of my own gelding. My guy went through some back issues and possibly ulcers (never scoped) that stemmed from a few issues (wrong feed, poor angles in hind feet, poor saddle fit). He wound up with recurring spasms in his back that would absolutely send him bat-crackers whenever he’d get the least bit tense or anxious about something. It was horrible. He’d always been my laid-back dude.
Someone mentioned sending the horse forward. In the end this is what finally pushed my horse into his more explosive behavior. He used to be a kick-a-long ride that, even if he did spook, it was in place and he got over it and life went on. I decided it was time for him to be “more forward” because he really was a plug, and eventually he was a nervous wreck under saddle AND on the ground. He would get anxious about a sound (something he hears all the time like the mowers mowing in the distance) and would literally tremble with eyes bugged out, neck held high (this is a western pleasure bred horse). I felt so bad for him.
He was adjusted twice by a DVM chiro, and he HATED it both times. She’s the one who diagnosed his back spasms. She recommended supplementing magnesium. That was no problem because I had ordered some Smart Calm Ultra which has 10g of magnesium. He started getting that the same day. A week later, he was noticeably calmer overall. More comfortable in his own skin, less distracted and reactive. The longer he was on it the better he got.
Next steps: find a saddle he liked. Even though the saddle at the time had been fitted by a professional, my horse still wasn’t pleased. He’s a good soul, so he tolerated it, but it was obviously still causing some issues. On a hunch, I impulse-bought a Wintec Isabell (I ride dressage) because of its much lighter weight and the way the panels are flatter to distribute my weight more evenly. He LOVES the saddle. So do I, thankfully. Whew.
Another major step: new farrier who specializes in barefoot and corrective trimming. She’s amazing and has made such a difference in his feet and overall well-being.
Final step, with everything going well from the steps above, I worked him pretty regularly and began really expecting more. All was good until one day it felt like both of his hinds had gone “flat”. It was awful. I’d never felt anything like it. Got the vet involved and discovered arthritis in his hocks. He was bad enough that he couldn’t even lay down (he’d try, it wasn’t happening). The decision was made to start him on daily Equioxx immediately and his first series of Adequan shots was ordered. It only took a few days on Equioxx to notice a big difference and to see him finally lay down. About 4 shots into the Adequan series, and just the difference in him being led in from the pasture or turned around in the cross-ties was amazing. He had always been one that you had to drag while leading and who was sooo stiff to turn around in a tight area. That was all fixed with Equioxx and Adequan.
I say all of this because there is something about your horse that, while he’s much more severe, does remind me of my guy. The scooping, thrusting thing with his penis is weird for sure. My guy drops a lot, and especially when I’m tightening up his girth at the mounting block. But he puts it away once I’m on and we’re working. So, that part is definitely different. But if whatever is going on with him to cause that is also causing muscle spasms and pain elsewhere, I would definitely suggest a bute trial to see if reducing his pain helps.
I’d also strongly suggest, just because he does look so tight/tense over his topline, to add some magnesium. It won’t hurt anything and just might help. My guy is on the Magnesium 5000 by MVP now. I have been double dosing him to get that 10g (he has mag in his ration and forage balancers too…so he’s getting more like 14+g of mag). I cut him back to one scoop this week just to see how he did, and I swear that even though I haven’t ridden him, I can tell just leading him that he’s a little more sluggish and reluctant and tight again. So, back up to the double-dose he goes.
Anyway, sorry for the novel. I’ve been following this thread, and I hope you can figure out what’s going on with him. It can be so frustrating, I know. Best of luck to you!