Weight carrying capacity in horses - some science

[virtuallyhorses]

Hi folks - I know we discuss this a lot so I was very interested in an article that looks at the issue published in 'The Horse Interactive" by Karen Briggs (who also wrote "Understanding Equine Nutrition" and "Understanding the Pony")

To summarise the most interesting stuff came from conformation analyst Deb Bennett Phd of the Equine Studies Institute. For those of you looking for high weight carrying capability here is your list:

- Excellent loin coupling - broad, short, smooth and strong. The circumference about the loin and groin should be about the same as the heart-girth
- short to medium length back
- moderately high withers with a peak that lies well behind the horse's elbows
- A pelvis that constitutes at least 30% of the body length and slopes from 18-22 degrees
- total body weight of less than 1450 lbs \ 658kg

They also noted that few tall horses fit these criteria and that heavy horses don't necessarily have a greater weight carrying ability since the density of bone isn't proportional to increased mass of the horse.

It is this combination that means that the shetlands, icelandics etc have their great weight carrying ability. In particular when looking at the horses which are renowned for endurance and weight carrying - its the broadness of the back and loins that mean the most.

I thought the upper body weight was a particularly interesting statistic. It is at that point that the whole 20% of body weight guestimate falls apart apparently.

[Stella2]

It is very interesting, but I do wonder about the referrence to heavy horses - if by that they mean draft horses. Natural selection should have left them with good bone and very good weight carrying ability, since when the draft horse lines were being established they were expected to pull considerable weight and the weak would have been 'weeded out'. Also they do tend to have broad backs!

[hApPiNeSs]

hehe not meaning to be picky but a lot of weight carrying ponies and cobby types have extremely low withers ;)

hehe i believe the rest of it though. happys back is short and overall she is very "compact" :)

[Retty]

Max is kinda square shaped, he's a Clydesdale x cob and seems quite a weight carrier, his back is I would say of average length but he is very wide with big shoulders, a big bum and overall very, very strong. Neither myself or my sharer are huge but we are certainly not of Kate Moss material. :D

[KarinUS]

Thanks for sharing that info. We were going by the 20% rule and falling somewhat short of it. Going by your criteria however Missy seems much more suitable for carrying OH than we thought.
She is broad, huge muscular butt, 1200 lbs and she even has the funky withers- unusual for a QuarterHorse I thought. I only wish her back was a bit shorter

[Yann]

That's the thing with draft horses though, they were bred to pull rather than carry, hence the upright shoulder and big front. I've read elsewhere that they're not automatically great weight carriers, though size obviously has an effect.

The description is interesting, Rio appears to fit most if not all of the criterion, including the weight limit, though the most we've ever put on her is about 12st.

[Wally]

Virtually horses....you used the word withers in the same post as Shetland and Icelandic......errrr, I've never found any, Cymro has some, the rest???????:( :( ;)

[tasha]

What do you mean by The circumference about the loin and groin should be about the same as the heart-girth ? Might need a diagram if that is at all possible (Im a visual thinker!).

[Yann]

May be wrong but isn't it the depth of the barrel just behind the wither and just in front of the hindleg?

[virtuallyhorses]

Originally posted by Wally
Virtually horses....you used the word withers in the same post as Shetland and Icelandic......errrr, I've never found any, Cymro has some, the rest???????:( :( ;)

Yeah ok I thought I might take some stick for that :) However, the criteria are not mine and I guess that with shelties and Icelandics it's the other criteria that matter rather than the 'moderateness' of their withers :D

Everyone who's mentioned horses with large bums - that's not a criteria, large bum does not necessarily equal strong loins! BTW there was one that I missed typing about neck conformation too.

With regards to heavy weight horses and capacity of rider weight - it's about bone and expectation. As said by Yann - these very large horses are bred for pulling not carrying. When used as a riding horse, there is an expectation of faster, more suspended gaits (trot etc) which create more force on the legs. So the bone mass in those legs is important when it comes to weight carrying and soundness.

A TB for example may weigh 550-600kg and have 8 or 9 inches of 'bone' beneath the knee - however larger breeds don't have the same skeletal mass ratio by weight. Very large horses may weigh 1000kg or more but this is muscle. Even the sturdiest may have only 10 or 11 inches of bone, in order to be the equivalent of the TB in weight bearing capacity these horses would need 16inches of bone or more! and no horse has this . So you can see that they are not made to carry great weight (plus a rider\packs etc on their back) and esp at any speed above walking where force increases markedly.

[KarinUS]

okay, then explain the 30% pelvic in a little more detail for those of us that assumed pelvic meant that it was part of the butt.
I understand that the loin would be more like the waist than the bum.
But if pelvic is not part of the bum where is it?

[virtuallyhorses]

TAsha, from the description I'm assuming that these are the two areas they measure

the heart girth being that circumference just behind the elbow that you measure for body weight.

and the loin\groin being the area that would allow you to measure the broadness of the back at the loin .. (I guess)

[KarinUS]

Yes, I understand that part. The point that needs explaining is the 30% of the horse's length should be pelvic area.
I figured it meant 30% of the horses length should be 'hind end'.

[virtuallyhorses]

They didn't explain the pelvis one very well but I assumed that they were referring to the pelvis as a structure which is judged externally by the classic conformation triangle.

My previous comment about 'big butt' not being one of the criteria was just trying to make sure that people were differentiating between bone\muscle structure and a generic 'big butt' which could be lots of fat or could be large but not 'strong' if the proportions\conformation aren't 'correct'...given that they also give a specific angle for the pelvis

Apparently these ideals for weight bearing come from Principles of Conformation Analysis by Deb Bennett perhaps we'll have to see if we can find a copy somewhere to check what she means.

[tasha]

Thanks, Viv!