LTR Hypoplasia - Nature, Nurture, Bit of Both?

Heads up: Long story (to provide background/context) with a sad ending. Opinions wanted.

I’m on second homebred generation and have run into a major health issue - and am very motivated to better understand the heritability, cause(s), and whatever else I can do better in the future.

Grandma Mare is a jockey club TB. I bred her to lovely WB stallion from a highly respected breeding facility. (Additionally, this stallion has a good OCD score indicating he is unlikely to pass on OCD. You may see where this is going.) Grandma Mare is still with us, but will likely be euthanized this fall at the age of 29 due to advanced arthitis in her front knees. (She started life with early racing followed by barrel racing. Ugh.) Otherwise, Grandma Mare has lived a long, sound life with no indication of heritable issues.

Grandma Mare produced one foal for me by the lovely stallion - let’s call the foal Heart Horse. Heart Horse took after her sire and has been a solidly healthy, sound, beloved mare. When Heart Horse was about 13, I decided to breed her (I would love a clone of her, but a foal from her might be the next best thing). I bred Heart Horse to another (unrelated, naturally) lovely WB stallion from a highly respected breeding facility. (This stallion, also, has a breed OCD score indicating he is very unlikely to pass on OCD.) She didn’t take the first year but did the second year, and foaled a handsome colt.

Handsome Colt had some tendon laxity at birth, being ‘back on his heels.’ Heart Horse also had this at birth to some extent, but hers self-corrected within ~48 hours. Handsome colt remained significantly back on his heel bulbs. We eventually opted for glue-on foal shoes with heel extensions to correct this, and he responded wonderfully to the shoes. Our farriers and vet worked together to keep the corrective shoes on through 2-3 shoeing cycles as he grew. Afterwards, his angles appeared solidly corrected, he went barefoot with regular trimming, and seemed to have no issues. Handsome Colt continued to mature into, well, a VERY handsome colt with a teddy bear personality.

At about 10 months, Handsome Colt presents with swelling in the left stifle. Big sigh - he’s a very large (mom is big and tall, dad is big and tall), gangly, fast-growing yearling. Gosh darnit I may have been heavy-handed with the grain over the winter. OCD diagnosis fits like Cinderella’s glass slipper. Local vet comes out and we radiograph the left stifle in the barn, and see a low-density area that looks like an OCD. Local vet refers us to state university.

We get an appointment about 6 weeks after initial radiographs at state university and bring in Handsome Colt. Vet at State looks at him and agrees, yup - likely OCD but don’t panic - they do a gazillion OCD surgeries every year, prognosis is very good, we caught in early. Books him in for OCD surgery the following morning. Pre-operative radiographs reveal we are not exactly dealing with OCD. Instead, we are dealing with severe lateral trochlear ridge hypoplasia. The ridges that should align and track the patella are… gone, basically. Surgery is cancelled, as there is literally not enough bone left to work with. Stifles are basically crumbling. The left stifle’s “skyline view” image of the trochlear ridges is described as a “ski slope,” and he could luxate the patella with one goofy step at any moment. The right stifle is similar but not as far along the progression. Hocks showed no OCD. The vet is on-board with us to try to maintain some level of pasture soundness with him, but early arthritis is basically guaranteed. Handsome Colt is brought home, where he remains happy for the time being. He’s in a pasture with a buddy, on Equioxx, I’ve already run one course of Adequan, and I’ve orderd “KER Duraplex” because I don’t know. Fortunately, I have my own farm with plenty of room, so I’ll try to keep him comfortable as long as I can.

SO. My theory is, I didn’t get the glue-on corrective shoes on early enough, and he slammed around too much too hard on soft little baby stifles recieving force at all the wrong angles. I’m absolutely gutted that possibly my overly-conservative management approach to this may have doomed my colt. There seems to be little/no family evidence of OCD, though perhaps it could sneak in from the TB mareline or just be a sad fluke.

What do you think? Have you every encountered anything remotely similar? Would you even consider re-breeding the mare, to a different stallion? (Not that I am planning on doing so in the forseable future, more a hypothetical question.) Would you interpret this as an OCD-like condition, with some genetic basis? Would the propensity to produce offspring born “back on their heels” with lax tendons be the deciding factor for you? Would you continue to maintain a horse who has some very real risk of luxating a patella at any moment, or would the risk of that occurence be enough to prompt euthanasia?

Maybe this article can answer some of your questions:
https://beva.onlinelibrary.wiley.com/doi/epdf/10.1111/eve.13390

It sounds like a sex-linked trait (all colts that were affected). It also appears to be recessively inherited in ponies.

I think you would probably be okay breeding to a different stallion.

At any rate, I am very sorry. I don’t think this is something you could have foreseen or prevented.

I would find it very difficult to euthanize because he is not currently suffering. But I would certainly worry about him luxating when you aren’t around to intervene. Did the vet that examined him recommend euthanasia? You can always euthanize at a later date when the arthritis progresses.

I would probably go ahead and re-breed the mare, and have a plan in place for your next foal in-case something goes wrong. Maybe breed to a smaller stallion, and try to avoid a rapidly growing foal.
If it is a recessive trait that only presents under the right environmental conditions, then I think your next foal will probably be okay.

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Ah yep - I’ve already read that paper (trawling the interwebs for resources since the diagnosis) and that is definitely the most similar to what we’ve got here. I can’t quite put my finger on why but those examples struck me as decidedly more congenital in nature. Both lovely WB site and grandsire have very large foal crops on the ground, and I could find not a smidge of this type of hypoplasia documented in WB circles. I just feel like if this was a thing, even a rare recessive thing, there’d be another one out there… I don’t know, something still makes me feel that there was an ‘early traumatic’ element to my guy’s diagnosis. (Though on the other hand, I could find no documentation linking tendon laxity at birth to later hypoplasia, regardless of corrective shoeing timelines.)

Euthanasia was certainly on the table in the discussion with the diagnosing vet, but in her words, “you can’t un-euthanize” so I don’t need to rush to that. His discharge report says something along the lines of “it’s reasonable to continue to support him medically” and that it’s encouraging he remains bright and fairly comfortable for the time being. I do have him in a somewhat larger pasture than the vet would probably like, but the footing is good and it gives enough room for him to loaf with his favorite buddy. (They picked at each other too much in the smaller paddock I tried first.) I guess I’m aiming for quality of remaining time over quantity. The vet was understandably reluctant to give long-term predictions (aside from concluding no athletic potential) based on lack of similar cases in the literature. I do realize that his young joints are not yet feeling the ravage of the impending arthritis just yet, and when they do, QOL is probably going to decline regardless.

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I am sorry you are dealing with this. What an unexpected turn and not what you want to hear when prepping for OCD surgery. :frowning:

I have never encountered something similar. After all you’ve said, I would consider re-breeding the mare to a different stallion. I would not interpret it as an OCD-like condition. This is something else and it is likely your HC was born with this defect in the trochlear ridge. No, producing offspring born back on their heels/lax tendons would not be a red flag for me. Your last question, only you can answer. You are the one that live with him and knows him best.

Frankly speaking, even if there was a congenital issue that a very well known stallion was prone to pass on, you would never know. There’s not much transparency out there until people make a fuss. Have you contacted the stallion owner?

Are you suspecting the grand-dam because her daughter (HH) was born with some tendon laxity, and then so was HH’s foal HC? Tendon laxity is fairly common in newborns and typically self-corrects. That to me would not signal granddam culpable for HC’s issues.

What was HC’s management like from the time he was born until now? You mention he may have gone through a big growth spurt?

I’m with others, I don’t think this is something you could have prevented or known about. Sometimes, things are just not born right even when both parents are perfect; and, just because they are born that way does not mean it is a heritable disorder. Congenital does not mean heritable. I hope you can give HC a peppermint for me, that is such an awful diagnosis.

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How terrible. I’m so sorry. Breeding is not for the faint of heart.

I agree with others, I’ve never heard of a correlation between this and tendon laxity, and I even tend to deal with laxity quite conservatively without issue. This also seems to me to be congenital, though I think rare.

I think you are in somewhat uncharted territory is regards to inheritability. I think it depends on if you can gut going through this again with rebreeding if this does potentially occur again, even if the risk is low.

I would also allow HC to continue living a quality life if you are able to monitor him and catch a luxation of the joint quickly. But I’d certainly understand if you wanted to go the route that would prevent that. I think you are justified in either approach.

I’m really sorry you are going through this. If you happen to find any more information regarding the case, I’d love it if you shared. Fingers crossed for you all.

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My theory is, I didn’t get the glue-on corrective shoes on early enough, and he slammed around too much too hard on soft little baby stifles receiving force at all the wrong angles.

I very much doubt this, It sounds genetic (either inherited or spontaneous) as a particular structure did not develop on both sides.

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Frankly speaking, even if there was a congenital issue that a very well known stallion was prone to pass on, you would never know. There’s not much transparency out there until people make a fuss. Have you contacted the stallion owner?

I have not yet, but likely will - we just got the diagnosis a couple weeks ago and I’m still kind of processing/mourning. I honestly don’t think the stallions have had anything to do with this, no hard feelings at all towards the very professional stallion owners; I just hate to share the bad news. I’ve also been in just agony over the idea that something I’ve done (grain choices? timing of corrective shoeing?) could’ve been the thing that’s doomed Handsome Colt.

Are you suspecting the grand-dam because her daughter (HH) was born with some tendon laxity, and then so was HH’s foal HC? Tendon laxity is fairly common in newborns and typically self-corrects. That to me would not signal granddam culpable for HC’s issues.

Almost less like I want to point the finger at an individual horse in the pedigree, and more I want to question whether breeding for a big, long-lined, fast-growing phenotype, with the knowledge that the babies are/may be displaying tendon laxity at birth, and maybe wonder if those factors are not… indicative of the most robust individual? I don’t know, nothing causative, of course. Breeding the mare again in the forseable future is not really in the cards anyways; I don’t think I could stomach it if I produced a second baby with such serious issues.

I’m going to attempt to attach the state university’s radiographs, if that changes anyone’s answers. LH_4 and RH_4 are the “skyline view” shots.

I honestly think that comes with the territory of breeding large WBs. Tons of foals have laxity but I’ve never seen it result in this. If you were dealing with OCD and were questioning husbandry, I’d think absolutely, feed or environmental factors could be the cause. But I really feel this is congenital. I don’t think you are to blame.

To be honest, I was expecting a bit worse with radiographs. I’ve seen much worse in small animals. I certainly see the issue, but the rads make me lean more towards QOL management.

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Yes, I’ve had a GSD whose hip joints were flat as pancakes. She was stiff but kept her active and well-medicated until we lost her to hemangiosarcoma. Sometimes the animal just copes. Heartbreaking disappointment in a young horse though :frowning:

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