Biomechanics, Inbreeding & Breakdowns

Understanding pedigrees, inbreeding, dosage, etc.

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xfactor fan
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Biomechanics, Inbreeding & Breakdowns

Postby xfactor fan » Mon Dec 21, 2009 7:18 am

Before starting this new topic, I'd like to request that this be a Phalaris free zone.


There is a very interesting chapter on biomechanics in "The Nature of Horses" by Stephen Budiansky. The author is both a horseman, scientist and good science writer, and this book interweaves biology, archeology, and research on horse intelligence.

The chapter on stride, speed and the biomechanics of how a horse runs and what kind of stress happens may be of interest to anyone breeding TB's.

In brief, the leg motion of the horse is an inverted pendulum, and rate of swing in largely determined by the weight of the lower part of the leg. Decreasing the weight of the leg can increase the rate of the swing. Nature and breeding have already streamlined the leg structure down to skin, bone and tendons.

Sooo...

Have American breeders been selecting for lighter bone density in their quest for speed?
Does lower bone density predispose injury?
Is there a deadly combination of training, drug use (steriods are toxic to bones), racing horses young, and at high speeds that is fueling the high rate of breakdowns in American racing?

And if so, is the solution as simple as getting race tracks to write longer races?

Is there a connection between speed, bone density, bloodlines and breakdowns?

Why did Secretariat--who still holds records for two out of three of the Triple Crown races--retire sound? How did he manage to combine a high rate of speed and soundness? Did his leg structure of long forearm, and short lower leg contribute to his soundness? Should breeders be trying to replicate this conformation?

Happy holidays to everyone.

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Postby vineyridge » Mon Dec 21, 2009 7:34 am

The Northern Dancer curse is a heavy body on light legs. Or so it would seem.

Good topic. I'll be interested to see what others have to say.

Lately I've been wondering about the effect of the electric starting gate on breakdowns. Standardbreds have a moving gate, and I wonder what their ratio of knee and ankle injuries is compared to flat racing TBs.
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Postby Tappiano » Mon Dec 21, 2009 12:08 pm

I'm not sure how relevant this is, but there are an awful lot of thoroughbreds with offset knees these days. Regardless of how slight it is, it must have some kind of effect on how the horse runs and ultimately, their soundness.

I think the major trend for years has been toward the pretty pony. I guess that is the shorter, lighter boned horse.

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Postby Nessa » Mon Dec 21, 2009 4:29 pm

We know that Secretariat had unusual cardio and pulmonary systems. Secretariat was also a superb physical animal. He was muscular, had wonderful bone, and overall very well balanced. He had great control of his body, and such extension that he got the most out of every stride. Look at some of the stuff about him on Youtube, especially anything in slow motion and you can see how powerfully he engages each leg, and the amount of thrust he got. Unreal, add all of these things together you get a superior athlete. Along with the will to win and you get Secretariat, Man O'War, Phar Lap ect. These animals are epitome of the breed. You can try and breed for them but you probably want get one like them. They just turn up every now and then to amaze and tantalize us.

TBs have always had offset knees, suspect underpinnings, bleeding lungs and every other complaint that Modern TBs have today. Just go to TB Heritage or any other historical Thoroughbred heritage site and you will see that everything that we are dealing with now existed then. I have found articles from the 1700's and 1800's where people are bemoaning the lack of stamina and the increasing fragility in their horses, the same complaints as today.

I do believe that certain sire and dam lines beget lighter boned offspring, and have done so historically. The problem is that in America horses have been found to be getting taller and heavier(more muscular), for running over a dirt surface. The added weight and lighter bone has been a bad combination. Turf racng with its kinder surface doesn't require as much muscle mass and so the lighter bone hasn't been as much of an issue.

Poor husbandry in raising young horses, shooting them up with steriods and hothousing them for sales. Pushing two year olds at sales and then racing them as early as possible. Pushing three year olds to make the Triple Crown and giving up on them when they don't. Poor training methods don't help either.
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Postby dublino » Mon Dec 21, 2009 5:02 pm

Nessa for President

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Postby Shammy Davis » Mon Dec 21, 2009 7:38 pm

I'm in. Actually, I've not told Louis, but he has been confused and Phalaris is really a grass that grows on every continent except Anartica. :lol:

http://en.wikipedia.org/wiki/Phalaris_(grass)

That being said, Secretariat was a freak. We should throw him out of the equation and any discussion and look at Somethingroyal's other foals. We should do the same with other productive mares progeny who had the odd phenomena for a foal. IMO opinion we spend to much focusing on the freaks and should look more to consistently successful racers and their producers. It'll make comparison easier.

I know of one equine physiologist who suggests that the heart size and capacity can be increased 50% with quality exercise. If he is right, Big Red started with a little larger than normal heart. Phar Lap and Sham possibly the same. Remember in Phar Lap's case, the original trainer trained him as a juvenile on him on sand and up dunes.

Here's an interesting link, I found.

http://genome.cshlp.org/content/8/6/569.full

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Postby xfactor fan » Tue Dec 22, 2009 10:02 am

Increase in heart size from exercise has been know about for a while. In TB's don't they all get heart building exercise? Except for unraced horses?

I'd like to keep Secretariat in the mix because he did retire sound. Yes, he was amazing. But the question is what about his legs enabled them to hold up to the pounding they got?


Getting back to biomechanics--which is science not art.

Are there several ways to lighten the lower part of the leg?

1. Decreased bone density
2. Decrease circumference
3. Shorten the lower leg in relation to the upper arm.

Do the first two options increase the chances for catastrophic racing breakdowns?

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Postby Shammy Davis » Wed Dec 23, 2009 7:26 am

Xfactor posted:
. . . I'd like to keep Secretariat in the mix because he did retire sound. Yes, he was amazing. But the question is what about his legs enabled them to hold up to the pounding they got? . . .


As I recall, Big Red had multiple occurrences of laminitis as he aged. Founder finally killed him. He was a powerful looking horse, but the early stresses on his small hooves as a juvenile, IMO, may have led overtime to his demise.

Considering the excellent care stallions received at high class breeding facilities, his life may have been cut short. Lower legs and hooves are normally the weak part of the racehorse equation.

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Postby aethervox » Wed Dec 23, 2009 9:04 am

Shammy Davis wrote:I know of one equine physiologist who suggests that the heart size and capacity can be increased 50% with quality exercise. If he is right, Big Red started with a little larger than normal heart. Phar Lap and Sham possibly the same. Remember in Phar Lap's case, the original trainer trained him as a juvenile on him on sand and up dunes.


What's interesting about that is that the increase in heart size is greater in long distance runners.

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Postby Shammy Davis » Wed Dec 23, 2009 5:02 pm

Xfactor asked:
Have American breeders been selecting for lighter bone density in their quest for speed?


No.

Does lower bone density predispose injury?

Yes, of course, it does.

Is there a deadly combination of training, drug use (steriods are toxic to bones), racing horses young, and at high speeds that is fueling the high rate of breakdowns in American racing?

I've not seen data to show that the rate of breakdowns is any higher than previously encountered.

Do drugs, juvenile introduction, and high speeds increase the probability of breakdowns?
Yes.

And if so, is the solution as simple as getting race tracks to write longer races?


I'm not sure but I think we would likely see less injury.

Is there a connection between speed, bone density, bloodlines and breakdowns?


Discount bloodlines. You are sounding like a pedigree analysis. I've read a great deal on this subject and I have concluded that speed and lack of conditioning is the reason for the majority of injury to the distal limbs. Many trainers who have written on the subject discount bloodlines and place emphasis on the individual conformation.

Just my point of view, but this thread should focus on the distal limbs in beginning. Then move on from their. Maybe if we chose exceptional horses who had a significant conformation flaw and discussed why that horse excelled vs others becoming injured or non-performing we would get have a better perspective.

I remember Preston Burch in his book saying that he would never buy a swayback, but that he knew of many who had excelled athletically. That says alot about human side of the training program.

Here is something on bone density w/links:
http://www.ncbi.nlm.nih.gov/pubmed/10659317

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Postby vineyridge » Thu Dec 24, 2009 8:40 am

I recently bought a mare who had had 64 unsuccessful (in the main) starts. All of her lower joints were recently radiographed and they are perfect, even with all those starts. She has no arthritis, no chips, no old fractures, no spurs, no nothing. All of the spaces between the bones are even. The old racetrack vet who did the pictures said her joints were like those of an unraced five year, and she will be 10 in January.

She's been going barefoot for a couple of years, and the vet did mention that her front hooves were unbalanced to the inside. So the next farrier, not the one that has been doing her for the past six months, was asked to see what he could do to balance them off. His opinion, and he has strong ones, is that she will always have extra wear on the inside because of her front leg conformation.

Would that "off balance" front leg conformation have affected her racing performance? Farrier did say that it would not affect her use as a hunt horse, just that it would be very hard to keep her from excess wear on the inside of her hooves.
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Postby Matchemforever » Thu Dec 24, 2009 10:47 am

Viney,

That sounds a lot like a horse I saw a few years back now. In this case, it was a Tennessee Walker. Usual farrier just shod the horse for it to be comfortable with how it was. Substitute farrier came in and "balanced" all the feet. Horse went lame. Usual farrier came back and in time, got the horse "unbalanced" again but what that horse needed.

I wonder sometimes if in trying to get "perfect" feet what's best for a particular horse is lost in the equation. I don't know but what is norm for race horses? Shoeing for what's considered to make the horse faster, or what's needed for that particular horses conformation?

Re: Secretariat
I always wondered why he got laminitis. I kind of thought he was allowed to get too heavy. I've heard the Bold Ruler's were subject to arthritic issues but don't know if there is any connection with that and tendency to get laminitis. Secretariat looks now to me like a horse that may have had Insulin Resistance issues, but I'll admit that's probably a long shot idea. If a horse is IR, laminitis is a threat.

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Postby Matchemforever » Thu Dec 24, 2009 11:20 am

I'll go out on a limb with something I've been thinking about for some time but haven't had the time to get in depth on it.

With what Patuxet said about Natalma and the Native Dancer issues, and Viney about the Northern Dancer's and big body on small legs, it makes sense. Too much weight at speed on underpinnings that may have inherited weaknesses, is now prevalent in the TB through those lines.

In looking at the pedigrees of Bold Ruler and Native Dancer, you have both horses out of Discovery mares- ought to have helped in the soundness department. But Native Dancer is by Polynesian, also known to have soundness issues, I believe, and out of Geisha. BR's dam has some Domino lines too but Geisha wins hands down in that aspect.

With Domino and his get- and there are some really gutsy horses from that line and I do respect them- it's hard to find stories that don't include soundness issues. I know Domino was not, to say the least, trained well and it may be arguable why he had problems but in looking at pictures, to my eye, with those legs, it was probable. (YMMV)

You put Polynesian over the Domino and I think the recipe was set. Native Dancer was a big horse with leg issues, Domino was very inbred and some of his decendents inbred to him.

I didn't know about the leg issues with Natalma. Couple that with Viney's observation about bigger body mass on those legs and it makes sense. I've been saying for a while that most of these TB's nowdays tend to look like Quarter Horses.

A Quarter Horse is speed for short distances. You put that kind of body plus speed plus longer distances plus inheritable tendancies and the recipe is there.

I know that regarding Domino, I've heard, "What about Broad Brush?" Yes, he's Domino male line but that's about it. He's not inbreed to Domino and has a lot of other influences, including European. In any breeding stew, the mix may come up different and there will be exceptions.

And while Selene was a great broodmare, I'll always wonder because of the two Selene sons that we got in the U.S., both had soundness issues. Correct me if I'm wrong. Her great Europeon son Hyperion was by a different sire.

Raise A Native dam, Raise You, brought in some Domino again. Also brought back in Fair Play through MOW's son American Flag but what's interesting about that is that American Flag, according to the history I've read, was retired after breaking down at the track. So in a line known for durability, was he an exception?

OK, ready for the flak! :!:

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Postby xfactor fan » Thu Dec 24, 2009 12:15 pm

Matchemforever,

You articulate a very interesting set of ideas. I've long wondered about Domino. The great breeder Robert Kleberg from the King Ranch liked the Domino line for speed, but felt they had brittle bones. He aquired Bold Venture to use in his breeding program. Apparently Bold Venture had the speed of the Domino line coupled with durability. This information is from the book "Great Breeders" by Bowen (I believe) The chapter on Kleberg is up on google books.

Bold Venture's pedigree. Please note the Domino comes in from the dam side--Possible by Ultimus, not the sire line.

http://www.pedigreequery.com/bold+venture

Again coming back to biomechanics, one way to get speed is to lighten the leg--physics. Works the same in horses, pistons, and toys built out of Legos.

Do I think that all breakdowns come from Domino? Of course not. And I reject out of hand that any sire line and the Y chromosome are responsible for all breakdowns.

But something to explore is whether in a quests for speed breeders have accidentally been selecting for short cannon bones, and low bone density.

As for Secretariat, I thought they let him get way to heavy, and this was the root cause of his foot problems.

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Postby Matchemforever » Thu Dec 24, 2009 12:55 pm

xfactor fan,

I do believe that there are exceptions to every rule and even an inbreed horse with lines with reputations for unsoundness is sometimes a sound horse. If breeding were not just rolling the dice, all horses could be sound horses.

But light bones for more speed- seems to correlate with the idea that stayers stay sounder but are not as fast, so probably more bone.

I do not equate short cannon bones with soundness problems. If anything, looking at pictures, I think we now have horses with longer cannon bones, higher knees and hocks, and a downhill build with the stifle higher than the elbow, IMHO. In general, I believe that horses with lower-set knees and hocks are becoming a thing of the past, right along with soundness.

I was looking at a picture of The Tetrarch and am always amazed at his hind legs. A description by a trainer praised that hind end for speed and power but at what cost? Compare him to Man O' War. Conformationally, I think MOW has a better hind end and at least in the picture on TBH, The Tetrarch seems to have hocks higher than his knees.

Is a post-legged hind end conducive to speed but also to soundness issues?

Have TB breeders shied away from low-set hocks and knees and why, if so?

I am still chewing over the idea that here in America, the perfect storm, so to speak, was created with the Polynesian/Sickle sires used on something Europe didn't have- Domino lines. I do not believe that it can be just as simple as one sire line. I do think that when you have an inbred dynamo, like Domino and some of his decendants, there is a reason the speed carries through but also a reason perhaps another trait carries through also. Combine that with perhaps like traits in the two imported brothers with increased body mass and it would seem to set up for problems down the road.

But hey, it's just a theory. :?: