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Horse suddenly unstable in trailer

My horse is suddenly experiencing some difficulty trailering that the vet cannot explain. I’m wondering if anyone has seen anything similar or has any outside the box ideas. Here are the facts:

Starting in late November or early December (a dozen or less trailer rides ago), I noticed ruckus in the trailer on turns, like my horse was scrambling. Eventually I figured out it was only on turns/curves to the right.

After this happened a few times I rode in the back to watch and video while someone drove figure 8s for me. What’s happening is bizarre and hard to explain, so I put a couple videos on YouTube (sorry, I didn’t have the means on hand to combine them into one video):

For those who don’t want to watch, here is my explanation. He’s not slipping (which explains why more bedding or less bedding, both of which I tried, didn’t help). It seems like it starts with him refusing to load his right hind and then sometimes even picking his right heel up off the ground. Then as the turn continues his hips sometimes fall to the left so that he leans on the trailer for a second. Or he steps to the left with his left hind and leans straight back. Sometimes he leans back and his knees bend, almost like he’s trying to sit down or starting a stretch. Sorry, hard to explain, like I said. But it’s definitely not just slipping. And like I said, he is totally stable and normal on left turns. It’s just when we turn to the right.

More details:

    Speed doesn't make a difference. I can creep out of my driveway at 2 mph or take a gentle curve in a 40 zone at 25 and still hear him back there.
    It does seem to get better the longer he is in the trailer, although my sample size is pretty small. When I drove him ~50 min to the vet on surface roads he was pretty steady by the time we got there and then again on the way home the same day. To/from lessons 10 min away is the worst and I cringe on every right turn/curve. This weekend I drove him home 2 hours (mostly highway) and only felt it three or four times, even when we got to the windy surface roads near home.
    Riding or turnout before shipping doesn't make a difference.
    Nothing about the trailer or rig has changed.

He was flexed in early Jan and only his right hind hock was very slightly positive on asphalt, which is pretty good for an old man I guess. His flexion was exactly the same back in 2011 and he has never been off on the right hind under saddle. He does get Cosequin ASU every day, Adequan once a month, and hock injections as needed but not super often.

I showed the vet the video and he agreed it’s very strange but said those things can be very difficult to diagnose and he would rather rely on the flexions and other clinical findings. (Totally understandable.) We did test him for EPM because of his history (see below) and his levels were so low that the vet said they do not indicate a current infection but rather residual antibodies from his prior bout. The vet didn’t see any signs of pain or tightness in his back and spine, so he said he wouldn’t recommend a chiropractor but that (or acupuncture or massage) is something I would consider doing if I thought it would help.

Here is info about the horse:

He is an 18-year-old Bavarian WB dressage horse, successfully showing at Grand Prix and totally sound under saddle.
I’ve had him since he was 4 so I’m familiar with substantially all of his (extensive) medical history. Here are the highlights:

    Spring 2002: While recovering from a torn suspensory, was treated successfully for EPM. Had obvious symptoms like imbalance/weird gait when walking downhill, that have never returned.
    Fall 2003: Scared the life out of me by putting a front foot through a straight-wire fence that went almost all the way into his coffin joint. Had emergency surgery and has fully recovered except for a scar. (It was hard to find barns without wire in Texas, but I went out of my way for wood fences after that.)
    Spring 2006-Fall 2008: Bone cyst in left shoulder, which required three surgeries. Resection of the bicipital tendon was finally successful and he has had no problems at all in that shoulder since then, even while moving up from Third Level to GP.
    Summer 2014: Slightly positive Lyme disease test. Vet did not recommend treating at that level without clinical signs. I only got him tested because he was feeling a little duller than usual and I am being treated for Lyme so I'm overly suspicious.

I keep him at home now so I know that nothing has changed with his care or routine. He has been totally normal and happy in every other way. Good boy even still self-loads without protest, even though I wouldn’t blame him if he didn’t want to get in there.

I’m wondering what could cause this instability without affecting his general soundness or well-being. I’m very curious to hear if anyone has any ideas! Thanks in advance.

I don’t have any ideas on the cause, but have a suggestion for you that worked great for the scrambler I used to have: tie the divider over or remove it. My mare would stand with her back legs spread apart and never scrambled at all when she could. The downside is that it turns your trailer into a one-horse trailer. From what I could tell, my horse was anticipating the turns (possibly by watching through the front window) and leaning too far into the curve.

Thanks, I was thinking of trying that too but since he’s leaning on the side and divider I’m also a little worried he will fall over if it’s not there! The divider doesn’t go all the way down to the ground so he could still brace with his hind legs pretty well if he wanted to.

Anticipating the turns by watching through the front window…pretty clever! Maybe a blindfold would have done the trick too. :wink:

My 5 yeard old standardbred started scrambling/ falling in the trailer… Turns out it was EPM. Even after treatment he still can not trailer… we had to sedate him and lay him down for his last trailer ride from where he was stabled to my home 4 miles away. I promised him NO MORE TRAILER rides as you could see how terrified he was

I had a gelding who did this also.

  1. He was used to hauling on the left and I had switched him to the right side.

  2. I had just bought a new trailer that had a divider that went all the way to the floor.

I moved him back to the left side and we modified the divider so it was just along their bodies and he could spread his feet for balance like he was used to doing and it never happened again.

He could be having a panic attack of sorts or have a physical issue that is keeping him from balancing the way he used to.

Check his ears for signs of ear infection as this can cause balance problems.

Maybe his stifle doesn’t lock on that side? It’s a pretty common injury, they can sub lux the stifle in the pasture and the ligament stretches enough that it won’t catch. I’ve had a couple, we injected the ligament with iodine to thicken it up, worked in one but didn’t work on the other - he was a little wobbly in the trailer and the vet said if he was going a long distance he would need a box stall so he could lay down.


FWIW, when my mare was still barefoot and I was doing the trimming, my formerly confidently self-loader suddenly became reluctant. Since I trailer her alone, I even removed the divider (she went from “coach” to “First Class”). Still reluctant… finally we figured out that my trim job was just a few millimeters off, so her hooves were a bit higher on their medial side. Once he trimmed her, problem solved. It was around that time that I decided to put shoes on her and the problem has never happened again.

so, maybe draw your farrier’s attention to your problem and ask him to double check the trim. Can’t hurt, might help.

Check your trailer. Something underneath may be cracked or broken, a brake dragging or uneven braking, tire out of balance, varying inflation pressures between tires or wheel out of alignment on your trailer or even the rear of your tow vehicle.

Once they feel unsteady because of these things, it scares them and they tend to over react to any hint of it happening again. Maybe it’s not him, it’s your rig.

EPM? Lyme? I would get a good work up by a vet school internal medicine vet or surgeon. Show them your video.

Did you change his shoes? Are your mats slicker than they were in the summer?

“Scrambling” around turns can very often be minimized or solved as other posters have suggested, by swinging the divider over to give the horse more room, or removing it altogether.

Needless to say, careful driving is essential!

I bought a mare several years ago who rode fine a few times in my Brenderup, then started scrambling on corners. I ended up trading the trailer in for a slant load and she was happy with that.
My assessment: brender up did not allow her to get a comfortable stance. She was leaning HARD on divider, scratched outside of hock on the edge where liner stops on the wall. That divider went to w/in about 2 feet of the floor.
Could a different straight load helped? Probably, but when I took her in friend’s slant it was great so that’s just what I chose.

Physically, I’d consider cervical arthritis, it may be brewing in early stages and not causing other signs yet.
I would also try taking him for a ride in a different trailer where he can stand in different position.

He’s a scrambler, and it’s a learned behavior that is very difficult to extinguish, such as weaving or cribbing. You can haul him in a larger compartment so that he can’t lean. When he has nothing to lean on, he won’t scramble.

It’s very strange that this is a new behavior.
I had a gelding who would scramble terribly when hauled on the left side of the trailer, but was 100% fine when on the right side. We started putting him only on the right side and the problem went away.

My second horse started similar behaviour when he was 10 or 11. Giving him more space so he could widen his stance meant he didn’t have to lean on the wall/divider any more, which meant he didn’t lose his balance when a turn pushed him off the wall.

My current horse started acting odd in the trailer - leaning on the back, bracing his legs and stuff last year. Tried giving him more room, but he stood on the trailer and shook until the divider was swung back. Quite by accident we discovered that giving him 5 or 10 minutes to stand on the trailer before we pulled out solved the problem completely. Now I wait until he shifts his feet after loading before we go. Once he’s comfortable moving his feet on the trailer he’s fine. He self loads too and has had no issues going in.

If he is leaning he then cannot spread his legs. If you have cushions they lean and squish the cushion and can’t spread their legs.

I have a diagram about removing the cushions and replacing with ski bars if you are interested.

Thos syops the hips going over to the side so as they xan spread their legs.

Another horse I had was not a scrambler but he did scramble one day to a ODE.

He also went through a showjumping fence with only one rail without even trying to jump.

Then each time we went out showjumping he pulled a rail.

One treatment from a chiropractor I trusted and he was jumping clear again.

Mine does this and it is incredibly frustrating.

We lost the entire season last year after we got to NJHP and I opened the trailer to find what looked like a scene from dexter… he had peeled off one of his front shoes (with his other front hoof) and jammed the clip into his foot in so many places there was a pool of blood on the floor and blood EVERYWHERE from where he was flinging it around.

For those who suggested sliding the divider over - I wouldn’t do that again. We lost 7 months out of the 2013 season when I tried that and he decided he would turn himself around to unload in the little tiny space it left. It was so fast I couldn’t stop it. He got himself a roachback/ hunter bump and well over a thousand dollars worth of chiro/acupuncture/vets visits after that.

He travels perfectly with his best buddy or in a big rig (4h or more) or in slant load.

It is purely psychological - He can go in the 2h straight load with his best friend and he will not move a muscle, happy as a clam. Alone on a (literally) 10 minute ride he got himself worked up into a full body lather on a 15 degree day last week.

It’s a damn shame because this horse has the potential to be a real star if only I could take him someplace without him trying to murder himself on the way.

I went straight to ear infection too but I’m not so sure that’s it.

Have you tried different trailers? He “feels” like he wants to be set up differently, at an angle or in a stock, maybe backward. It’s like he wants to lean one way but he can’t. If it’s a learned behavior maybe a different set-up would help?

I have no experience with EPM/thelike so I can’t say much toward that but if what I said didn’t help I would be looking at that.

Can you do a little drive with him on the wrong side of the trailer?

It looks like he doesn’t want to touch the divider, so won’t lean on it. I wonder if you stick him in the wrong side of the trailer if he’ll suddenly have problems with left turns.