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Ben Tyndall
Member
| Posted: Wed Dec 3rd, 2008 01:28 pm |
I certainly have some muddiness on this topic of bone size vs horse weight. I have not read the Equus article mentioned by Dr Deb. My question for Tom's engineer friend: Regarding the statement "Load depends on the area", is the relation between cross section area and load bearing capacity linear?
My guess is that for substances like steel and concrete cylinders, the answer would be yes, but for the bones in question perhaps not, given that we're talking about a combination of bone, tendon, skin, hair, blood vessels and maybe other stuff (marrow?).
I think the relationship between circumference (which is what we typically measure on the horse) and cross section area (which tells us about load bearing capacity), to which Tom alluded earlier, has to be somewhat significant in this. If circumference is increased by x, the area will increase by x-squared, so the relationship is not even close to linear.
...Ben
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AdamTill
Member
| Posted: Wed Dec 3rd, 2008 04:21 pm |
Hi folks,
Maybe I can be of assistance (mech eng by training, though I haven't done much of it in the last few years).
You're probably best to look at buckling, since we're dealing with thin columns for the most part. See: http://en.wikipedia.org/wiki/Buckling
From:
http://www.springerlink.com/content/v674tvt57gr4t62l/
and:
http://en.wikipedia.org/wiki/Young%27s_modulus
...we note that we're probably dealing with a substance that falls somewhere between wood and concrete in most mat'l properties. If you read the wikipedia entry for where thin beam buckling applies, we're probably not far off in assuming that this is valid.
For simple buckling, force at failure is proportional to moment of inertia. A nice simple calculator here:
http://www.engineersedge.com/calculators/section_square_case_12.htm
Can be used to get that for various thicknesses.
For that 2000lb draft horse mentioned, Dr. Deb's findings indicate that draft horse likely has about a 10" cannon dia. Let's assume for argument that's all bone, and has a wall thickeness of 0.25" (inner dia of 9.5"). That gives I=90.9 according to our calculator.
The guideline says we should be up at 16" dia, however, so let's scale up to the same proportional wall thickness and use a 15.2" ID. That gives I=595, or about 6x the buckling resistance. Makes you think.
I found it amazing that my new Icelandic @~1000lbs and 14hh has a dia measurement of 9", where my old 17hh Holsteiner was 1400lbs and only 10.5" dia. Reading that Wiki entry also reminded me that the shorter leg length factors in favorably as well, since short columns are less likely to buckle (ie 16 hh and 1000lbs isn't the same situation as 14hh and 1000lbs).
For the really dedicated:
http://jeb.biologists.org/cgi/reprint/202/18/2495.pdf
Hope that helps in some way. I don't know if buckling is the best way to look at things, since joints will likely fail before the "beams"/bones themselves buckle, but it's an interesting excercise.
Cheers,
Adam
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AdamTill
Member
| Posted: Wed Dec 3rd, 2008 04:27 pm |
Ben Tyndall wrote: I certainly have some muddiness on this topic of bone size vs horse weight. I have not read the Equus article mentioned by Dr Deb. My question for Tom's engineer friend: Regarding the statement "Load depends on the area", is the relation between cross section area and load bearing capacity linear?
My guess is that for substances like steel and concrete cylinders, the answer would be yes, but for the bones in question perhaps not, given that we're talking about a combination of bone, tendon, skin, hair, blood vessels and maybe other stuff (marrow?).
I think the relationship between circumference (which is what we typically measure on the horse) and cross section area (which tells us about load bearing capacity), to which Tom alluded earlier, has to be somewhat significant in this. If circumference is increased by x, the area will increase by x-squared, so the relationship is not even close to linear.
...Ben
Ben, I'm not the engineering mentioned, but no the relationship isn't linear. Go to the calculator I mentioned above:
OD (outer dia) ID I area (units^2)
16 15.9 79.5 2.5
16 12 2195 87
16 8 3010 150
16 4 3198 188
This is proving the concept that, assuming it doesn't get so thin-walled as to buckle, a tube on average is much stronger in bending then a rod OF EQUAL MASS. Remember that mass increases dramatically with wall thickness, but bending strength doesn't match that increase. With increases in mass come increased forces as well, questioning again the claim that "bone density" is somehow a benefit.
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Jacquie
Member
| Posted: Wed Dec 3rd, 2008 06:06 pm |
Hi
This is a big 'drafty' horse, - part Appaloosa I think - which has been trained to a very high standard and who won at the World Para Dressage competition in UK last year. He is a bit keen in this pic, but his test was really soft and very obedient. His rider was very disabled apparently but I really could not tell what her disability was. She was brilliant.
Another comment I can make is the fact that I recently in October visited Andalucia for an educational riding break and was lucky enough to ride Andalusian and Lusitano stallions and all beautifully trained in classical dressage to be light and soft. One small dun Lusitano was very croup high indeed but I rode the lightest passage ever on him just by sitting taller and closing my legs. My 14 year old daughter rode him in passage too. He was fantastic and he was re-trained at a later stage in his career and had not had a good time before arriving at this yard, with the serrato scars still on his nasal bone to prove it. His remaining anxiety still shows up occasionally as lip flapping.
Training is key really and you can overcome most problems connected to your horses conformation or past poor training issues, but it may take you longer and require more skill and patience to train these kinds of animals.
Jacquie
Attachment: Copy of P1000325.JPG
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Tutora
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| Joined: | Fri Sep 5th, 2008 |
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| Posted: Wed Dec 3rd, 2008 09:47 pm |
Hi Rifruffian--You asked about bruised feet. I don't know the answer to your question, really, but I have a vague guess at what caused problems for my big gelding. Maybe I should have specified that all my horses go down a runway that has several bare tracks where horses go through different gates. They at least trot, and often gallop, down the hill. Though it's not steep, it sometimes has new rocks exposed after a summer thunderstorm. I've been here 17 years with my own small horses and a few boarders-- all barefoot--and have had no stone bruise issues.
...Until this year with my one big guy who's now 5 and nearing his full size. Aquila has good hoof conformation--good frogs, thick shiny walls, proper sole concavity, no flares at all, nice sized hooves,and good pastern and hoof angles. He's trimmed every 6 to 7 weeks without fail by an excellent trimmer. He lands on his heels.
He's an Andalusian/Percheron, and he's in between both breeds in looks and movement, favoring the Andalusian side in looks.
My guess is that since all the horses have a chance at hitting any given rock if they run over them before I pick them up, Aquila at a gallop has much more weight coming down on the same area of rock/sole junction as the smaller horses. And the added sole thickness in his larger feet isn't enough to offset the increase in force??? That's just my guess--I am surprised to be dealing with any stone bruises after all these years with no problems.
It's not an insurmountable problem--rather than go to shoeing him, I can save several pastures for him that don't use the bare downhill tracks if the problem continues. But the way my free access stalls/dry paddocks/pastures are set up, it's a bit of a difficulty. Aquila is funny and clever, and I don't regret buying him as a yearling--I just didn't know then that he might have some different issues. In another management situation or soil type, it might not be a problem...but I love where I live and I love Aquila, so I need to figure this out.
Any thoughts are welcome!
Jacquie--I was wondering how your trip to Spain went. Lucky dog!--Elynne
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Jacquie
Member
| Posted: Thu Dec 4th, 2008 03:39 am |
You're right Elynne - I was very lucky to go to Spain - and going to that particular establishment was definitely a good choice. Wonderfully trained beautiful horses that carried themselves - without reins to help them and needing only the lightest touches to communicate to them. Me and the girls learned more there in 5 days than we could have in 5 months of lessons at home because the horses taught us as clearly as the instructor did.
I am definitely planning to make a repeat visit next year - and my horses at home have really appreciated our newly refined style. At my previous rate of learning, I am not sure if I can live long enough to ride really well unless I take regular trips to places like this!
Riffruffian: I am not quite daring to go barefoot with my three horses, though my pony does and he is fine. The pony only goes out on the roads for a hack once or twice a week and otherwise he is ridden in our school. I am not quite confident enough that it will benefit the horses yet though. I know people here in UK who have taken their horses barefoot, but many of them have made their decision to do this based on economics - shoeing is expensive here - or based on the level of road work they have to do in thier area. I don't want to make the decision on the basis of finance and my hacking area is criss crossed with lanes and roads which I have to use to get anywhere. If I am convinced somehow that it is truly better for the horses and not just for my pocket, perhaps I will then. I have to do a lot of road work here though and although the field is not a problem barefoot, the roads may be. I do know that the Canadian mounted police are barefoot - but they probably mostly walk on roads and rarely trot. I still feel dubious about my huge footed Appaloosa becoming sore or having his foot break up, trotting on roads and cantering on stony bridleways so my 3 horses are rather expensively hot shod every 6 weeks for now.
Jacquie
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rifruffian
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| Posted: Thu Dec 4th, 2008 06:20 am |
Tutora thanks for those few lines of explanation relating to your biggest horse; I'm not convinced yet of that general idea, ( increased size of horse=increased risk of stone bruises) but still thinking about it.
Jacquie I am also UK resident (Scotland) and have kept my horse barefoot for several years. Some years ago my previous horse (now deceased) partnered me at endurance meets. He was shod but had one particularly badly conformed front foot that eventually would not retain a shoe for any useful period of time. Thus I investigated the barefoot idea and adopted it. We continued to participate in endurance successfully.
Because the barefoot experience had previously suited, I continued it with my current horse even though his foot conformation is good. My mind is not closed to shoeing if it seems a better idea in future. The idea of reduced cost was not originally considered, but I am the trimmer for my own horse and there has been reduced expense in that area over the years.
As far as roadwork is concerned my experience is that it does not promote excessive wear. I consider some travel over solid hard surface such as tarmac or concrete to be an essential part of the foot maintenance.
So you can at least continue to consider it....Patrick
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Jacquie
Member
| Posted: Thu Dec 4th, 2008 07:15 am |
Hi Patrick
Its nice to know your real name - where did you get the name of Rifruffian? Whereabouts in Scotland are you? I live in north Somerset.
You see, I am still doubting and concerned whether the the road work will be OK for unshod horses travelling at a trot on tarmac and/or rough stony bridleways such as we have everywhere here and I am wondering if you have more off road riding available - perhaps on moorland or softer, less stony going at least there. Does the 'right to roam' Scottish Parliament bill extend to horse riders too or is it only for walkers?
You are right though, I will certainly keep mulling the barefoot thing over and weighing it up. It is such a quantum leap to take initially though, especially if you have no issues with shoeing being a problem for the horses in the first place. I certainly would like to cut my costs - who would not - but I wont do it purely for that reason.
Jacquie
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Tutora
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| Posted: Thu Dec 4th, 2008 09:11 am |
Hi Patrick--I'm curious too about "Rifruffian".
I'm not being argumentative...I'm re-submitting my thought on any size/stone bruise connection because I want to figure out what caused my big horse's 2 stone bruises and therefore what I can do for him.
The stones here are bluntly pointed sandstone, and usually small. The point of impact between the rock and the hoof sole may be 1/2 inch in diameter, as an example. So in this case, the area of the whole sole is irrelevant, I think. Aquila, my big guy, has more force landing on the same area of impact as Tutora, my 15.1 hh Lusitano. Yeah, his soles may be a little thicker because his foot is bigger overall--but I'm thinking it's not as good a ratio between weight/sole thickness+ toughness as my smaller beasties. ---Elynne
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sunnyriot
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| Posted: Thu Dec 4th, 2008 12:55 pm |
>>So in this case, the area of the whole sole is irrelevant, I think. Aquila, my big guy, has more force landing on the same area of impact as Tutora, my 15.1 hh Lusitano. Yeah, his soles may be a little thicker because his foot is bigger overall--but I'm thinking it's not as good a ratio between weight/sole thickness+ toughness as my smaller beasties. ---Elynne <<
Wow, this topic is getting at the impact (pun intended) of the physics for sure. Without a thorough study on the subject we can't really know if heavier horses are harder on their hooves or not. While it seem logical, it is also a fact that hooves adapt to use. The added concussion should add thickness to the sole and wall -- in a healthy hoof. But I am not aware of any such study.
After all the discussion of bone, I wonder if bone size even has that much impact on soundness. The joints seem to be the areas of weakness -- we don't often see long bones snapping due to concussion. Even Eight Belles' fractures occurred in her fetlocks. It would have relevance if larger bone (or tendon) size determined joint strength or stability? But what would that relationship be? My guess is the the impact absorption function of the soft tissue is what is crucial here rather than the size of the actual bones. Meatier tendons probably do this better?
Good point about the bone density as well Adam. My engineer friend and I touched on this but seemed so unconcerned by the density of our imaginary pillar that I wasn't sure he understood my question LOL!
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rifruffian
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| Posted: Mon Dec 8th, 2008 12:33 pm |
Hi people, to answer these various questions......as a result of having spent some time in the Rif, an area at the north of Morocco, I thought of the user name rifruffian. The Rif is a 'wild west' sort of a place.
I live near Biggar, south scotland. 'Right to roam' legislation does apply to horse riders in Scotland so yes indeed we do have substantial moorland and hill country at our disposal.
As to the points made by Tutora concerning these stone bruises, there is not any arguement against the physics of it. The only other thing that occurs to me, so far not mentioned, is that presumably the bigger horse has (compared to smaller horse) larger sole area and therefore more possibility, in a single footfall, to 'capture' a stone and take a bruise. However, perhaps that large horse has longer stride therefore fewer footfalls over a given distance.
But the practical thing is to use area with few stones because even shod horses pick up stone bruises.
Patrick
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Tutora
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| Posted: Mon Dec 8th, 2008 05:53 pm |
I think that's a good point about the larger sole being more likely to snag a stone.
I have had more stone bruises when I had shod horses. Years ago I took my 3/4 TB barefoot on my farrier's advice, and once he developed sole callouses, he actually stopped getting bruises. I agree with Jacquie, too, though, that going barefoot can be scary, and may not always be worth it for every horse... but there are good boots available to ease the transition.
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Jacquie
Member
| Posted: Tue Dec 9th, 2008 01:25 pm |
DEar all
I just went back and read this post from DD and I so loved it I have copied it again here! I had not read that post when I was rabbiting on about how you can train any horse for any task but it usually takes longer (and is more technical) if it is a far removed task from the one the horse has been originally bred to do.
DD Wrote:
Now there is a fourth point to be made here as well, and that relates to "type". There are (I joke) five types of horses that we can recognize in first-world countries today:
1. Riding horse type
2. Race horse type
3. Carriage/harness horse type
4. Draft horse type
5. "Projects''
That is so right! I am going to use that statement!
Bruised soles do happen with shod horses too, but not that much - unless you have a very flat footed horse like Thoroughbreds often are.
I feel cautious about this subject as with all the diverse kinds of hoof structural issues and all the variations of riding terrain makes this a very complex decision.
In short, I am not sure that every horse can go barefoot and stay sound.
just my thoughts
Jacquie
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Tutora
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| Posted: Tue Dec 9th, 2008 04:23 pm |
Hi Jacquie--I don't think you took it that I was implying people who shoe their horses are wimps... but just in case it sounded that way, I'm sorry. I've had my horses barefoot before barefoot was a "movement". The ability to work unshod has been part of my criteria in choosing a horse, and I live in an agricultural preservation district with lots of fields to ride in, so I'm hardly an unbiased reservoir of experience in going barefoot with all horses in all conditions.
Having said that, for anyone thinking of giving their horse a try at going barefoot, your farrier might be able to roughly predict your horse's likelihood of success.
I've seen people -- whether their own horses are shod or barefoot--be really demeaning to other people who do the opposite... so that's why I'm trying to be clear that while going barefoot worked well for me, I don't know either if it's for everyone.
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Jacquie
Member
| Posted: Thu Dec 11th, 2008 01:27 pm |
Hi
No offense was taken at all from you Tutora. Maybe I am a wimp on this tho!
I am not sure if asking the farriers advice is a good idea as the farriers advice will not be totally unbiased - his livelihood depends on people needing horses shod...........
Wow Patrick Rifruffian - with your right to roam law, Scotland must be a really great area to live then for intersting riding! I have to stick to the bridleways here in North Somerset and if I deviate from the designated track the farmers would go berserk if they saw me! I take all the horses to Exmoor sometimes though for a little holiday and we go completely wild then, haring about at a gallop - all over the moor and in the woodlands! The horses love it! Actually last time I went, Fox lost a shoe on the last day and I had to walk home to our rented stables, leading him............................ho hum!
Jacquie
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