Article on thehorse.com about genetics of height

[wyeoakequine]

I’ve long hoped to breed my 16h ISH mare to a large pony one day to produce the smallish sport horse I want for myself… and then I read this article on thehorse.com and it sort of crushed my dreams.

Growing Up: Estimating Adult Horse Size – The Horse

I’m just wondering- is it really possible that the idea of a foal’s height splitting the difference between mom and dad is a total fallacy? From my perspective this seems to be a fairly widespread belief, and it’s hard to imagine it would persist if it really doesn’t work that way AT ALL.

I know there will always be exceptions… ie- my Oldenburg mare who matured at 15.1, with dam and sire both over 16h.

I want to ask, though, of those of you who have boat loads of personal experience: what have you observed regarding the height of the offspring of tall horse and short horse?

[fire_911medic]

A medium sized horse was what I was shooting for when I bred for my stud. The dam was barely 15 hands. The sire 16.3. I was shooting for around 15.3-16. I thought older mare (she was 20 when she foaled-perfect pregnancy). Along with being short I would get a mid sized foal. He was slow to grow and at four he was 15.2 which I was perfectly fine with. As a late four year old he had a huge growth spurt and is now pushing 17.1 and the smallest of his sire. The largest is 18.1. His babies are all huge leggy things but well proportioned and I have crossed a few smaller mares with him and babies may have been a touch smaller but we are seeing average height of 16-17 hands (the Arab cross was 15.3 the smallest and only filly).

[Dr_Doolittle]

[QUOTE=fire_911medic;7330736]
A medium sized horse was what I was shooting for when I bred for my stud. The dam was barely 15 hands. The sire 16.3. I was shooting for around 15.3-16. I thought older mare (she was 20 when she foaled-perfect pregnancy). Along with being short I would get a mid sized foal. He was slow to grow and at four he was 15.2 which I was perfectly fine with. As a late four year old he had a huge growth spurt and is now pushing 17.1 and the smallest of his sire. The largest is 18.1. His babies are all huge leggy things but well proportioned and I have crossed a few smaller mares with him and babies may have been a touch smaller but we are seeing average height of 16-17 hands (the Arab cross was 15.3 the smallest and only filly).[/QUOTE]

fire_911medic–did your stallion inherit the phenotype of HIS sire, rather than his dam? According to the above article, it would seem that foals will tend towards the height of the parent whose phenotype they inherit.

I would love to hear anecdotal evidence to this effect (or that refutes this theory–obviously “nothing is 100% predictable” when it comes to horses–or breeding); this is an interesting topic!

[arlosmine]

It’s much less predictable to breed extremes in type and size to one another. Rather than a blend of the two, you can get “Frankenpony”: horses head, pony legs, horse body, pony feet.

I have three warmblood X Pony crosses:

One is a Haflinger X Hanovarian. Han sire was about 16.2, Haffy mom was around 13.3. My guy is 14.2 and weighs 1000lb. His head is the same size as my 16.2 hand cob cross. (thank god it’s a cute head!) he has a longish, stout body on short legs. He is rather oddly proportioned, but correct work has muscled him in the right places, and he no longer looks like he is going to tip over and land on his nose. He has lovely big bone and big hard feet. BEST BRAIN EVER. He moves like a pony until you get him through his back, then he is much improved. He is the best school horse in the world since I can put tiny children and larger adults on him. He is fantastically trainable: not a world beater athlete, but I have made a personal project out of him because he is tries so hard. I will show him second level this year.

I also have a coming three year old Wesser Ems gelding. Fancy! His dam is a 12.2 hand section B welsh pony. Dad is DSF Farscape, a 16.2 hand Westfalen. yesterday I measured “Fig” and he is 14.1/2" at the wither. Right now he is level and looks almost ready to back. The string test says 14.2…but we will see. I may have a hony on my hands in a few years, but since my sport of choice is dressage, I opted to risk getting a little oversize, rather than under. If he goes “over” my back-up plan as marketing him as a hunter pony goes up in smoke. I have to wait until he’s six and gets a permanent card before I could ask real money for him in the hunter market, since he’s an F-1 cross and could well have a late growth spurt.
He is a more harmonious blend of horse and pony parts. He looks and moves like a small horse, with really good horse gaits. His walk, in particular is very nice…an 8 at least (let’s hope it stays that way with a rider on him!) His temperament is fantastic.

Finally, I have a Cob X TB cross. Mom was a 16 hand TB, dad a 14 hand Cob. This guy’s hocks, head, knees and feet were all so big when he was a yearling that he looked like a great Dane puppy. He was down hill forever. When he finally leveled out at five I thought he was done growing at 16 hands. Then he grew another 2 inches between his fifth and seventh years. I researched both parent’s ancestors, and found that the mare had two full brothers over 17 hands. The sire had some of the very tall Cobs a few generations back in his pedigree. All the latent “tall genes” in mom and dad got together for my guy. He has been a wonderful horse. We evented, showed in open dressage, went horse camping…you name it. Another stellar temperament.

So: it is a crap shoot! If you are needing a specific size, you are not likely to get exactly what you want. If you would breed your mare regardless of size, go ahead. I would look at the size behind the mare, and for sure breed her to a stallion with lots of babies on the ground to get an idea of what he throws.

Then there is the possibility of a frankenhorse… I love my Haffy cross, but if I was trying to breed for a horse for myself, I would have failed.

Good luck! Pony crosses are delightful

[omare]

Wow-I guess the pony people may have insight to that: how to explain the xx mare crossed with the welsh pony to get your large division pony if the dominant gene rules or does it? Or does environment (in the womb) also decide height?

[arlosmine]

Womb environment does not effect adult size/hight. There have been studies done on that one. small baby is born, but catches up to genetic size.

The hunter pony people most likely do a lot of research into the size behind the individuals to be bred, and even the pros get oversize larges. You just don’t hear about them.

[MysticOakRanch]

Yeah, I have to say, it is more of a crap shoot. As an example- I have a 15.3 hand Warmblood mare (Oldenburg/Hanoverian lines). She has 3 foals I bred. The first was by a 17.2 hand stallion, and that filly matured at about 15.3. The 2nd was by my 16 hand stallion - that gelding is 5 years old and in a growth spurt, he is about 16.1 and growing. The 3rd is a filly that looks like she’s going to hit 15.3 to 16 hands, so one out of three is averaging the parent’s height. To add to it - the first foal was VERY leggy and huge - she looked like the one who would grow the biggest - and she basically stopped growing at 2 years old.

Another mare I bred, 16 hand Dutch mare, has two foals by the same stallion who is 16.1, and those two kids are 15.3 and 15.2. Then she has a 16.2 hand gelding by a different 16 hand stallion. I bred her a couple of years ago to my 16 hand stallion, and that long yearling colt is already 15.3.

I could go on and on, but basically my experience has been seldom do you get the “average” of the parents’ heights.

[stoicfish]

http://horsetalk.co.nz/2013/02/22/key-gene-horse-height-identified-researchers/#.UrsUJXiA3UA

[Hippolyta]

In addition to infinite environmental influences, height is hard to predict b/c it is a typically a polygenic trait. Look at this pic (http://legacy.owensboro.kctcs.edu/gcaplan/lab/Image281.gif), but imagine that instead of skin pigmentation, each dark dot gave an extra boost to adult height. You can see how medium height parents could have v. short or v. tall kids.

Add to this the effect of regulatory genes (epistasis) such as the one in stoicfish’s link…predictions go out the window.

[wyeoakequine]

Thanks for sharing your thoughts, all! I felt the article I shared had to be oversimplifying it to some degree. (I’ve kinda felt The Horse has been watering down their stuff more and more recently- I remember it being a much more “meaty” publication ten years or so ago.) Perfect example pointed out by arlosmine… the article suggests that the foal will inherit it’s phenotype from either mom or dad, but how would we get “frankenponies” if it were that simple? Surely, we know that some mixing of the phenotypes is typical.

As an aside, arlosmine, your Haffy cross sounds like a gem. I love the fact that you love him for who he is! Maybe that seems odd to say, but I spent too long working for a breeder who couldn’t see the virtue of anything outside her strange image of perfection. It was only a year, but it was TOO LONG!

Thanks for sharing that link, stoicfish! I went through to the actual study to get a little more info, as I was confused by what might be an error in the summary. It says both smaller and large warmbloods are homozygous for the mutation. Maybe I’m missing something, but wouldn’t it make more sense if large warmbloods were homozygous for not having the mutation? That’s what I got from sifting through the study.

In any case, it’s interesting that the heritability of height is documented stronger in ponies, though I’d think this would apply less to the sport ponies with warmblood in their background. I’d also wonder if similar heritability of height is seen in horses who are homozygous for NOT having the mutation- your super big horses. And with this model in mind, it makes sense why we see so much unpredictability when we breed horses of moderate size that are likely to be heterozygous.

[Daventry]

[QUOTE=arlosmine;7330890]

The hunter pony people most likely do a lot of research into the size behind the individuals to be bred [/QUOTE]

The big difference with the pony breeders is, height is being specifically bred for, so it becomes easier to predict, than for example, breeding a warmblood who’s parents and lineage may be a variation of heights.

It’s why many experienced pony breeders often recommend breeding to a purebred Welsh Pony stallion when breeding a crossbred pony mare…as the generation after generation behind the Welsh Pony stallion most likely has a consistent height pattern…so it makes it a lot easier to predict what the foal will finish at, height wise. Of course, there are always those breeders that will try and gamble a bit - sometimes it works, sometimes it doesn’t.

[Appsolute]

We purchased a 13.3 hand Connemara mare that was in foal by a 16.2 hand TB. The hope was that the foal would become a sport hony for my 5’1" sister.

That horse finished out just over 16.3 and was long as well, over all quite a big horse!

My personal horse is 16.3+. Dam was a 16.2 hand TB medium light bone, sire was heavy boned and 15.3. As far as phenotype, she really seems like a mix of the two. Medium heavy bone, neck heavier than her dam, but not as heavy as her sire’s, head more refined than sire’s, not as fine as dam’s, etc.

[wyeoakequine]

Wow, Appsolute- getting a 16.3 baby from a 13.3 mom musta been a shock! That’s pretty wild… but totally in line with the article from The Horse.

[RunningwaterWBs]

Over the years, I’ve noticed a few things about height. (Since I breed warmbloods, that’s what I’m referring to here.) These, of course, are only my opinions and are not the result of anything scientific!

1. Looking at the parents doesn’t tell you the whole story. Some ancestors have and pass on height, be it large or small. This can crop up at any time, regardless of the size of the parents. The more consolidated the pedigree is for height, the less of a crap shoot you will have.

2. Know your mare and what she ‘tends’ to pass on. I’ve known some mares, for example, who seem to have a sex-linked height pattern; colts tend to be in one height range while fillies tend to be in another.

2a. I am often suspicious of stallion height, having seen several listed as 16.2 or better who aren’t a hair over 16hh when you see them in person. I chalk this up to stallion owners trying to give their boys a chance, given the current thinking on warmblood height, which seems to be: 15-15.3=tiny/inferior*, 16hh=small, 16.2=average/ desirable, 16.3=big/good, and anything 17+hh= huge. When you think about it, ponies and pony breeders have a much larger acceptable range; anything from 10hh-14.2hh can “fit” into a division. Warmblood breeders have an ideal that is really a single hand: 16-17hh.

3. If you are selling foals or breeding for the amateur market, you need to know enough about the height of what you’re producing to at least give a decent guesstimate of adult height. IME, it’s one of the very first things most customers want to know. (Ironically, pros seem wildly less interested in height.)

4. Following on 2a, how official are the statistical heights that most warmblood breeders are looking at? Ponies get “cards” based on measurements made by show officials in the US. Granted, there’s some fudging done with creative farrier work, but the measurement can’t be all that far off. Conversely, although I’ve seen some measuring sticks held up at mare inspections, often the mares won’t let the stick get close to them in those situations, so WB breeders have to rely on mare owners’ own height-taking abilities.** Sometimes this is based on a complete guess – no stick involved – or done improperly. If official heights are taken at stallion tests, how often do those heights correspond with what’s on the owner’s website?

I’ve found that height is a really strange thing. It’s surprisingly much more of a grey area than might be supposed, yet it’s also extremely important to many buyers.

• I say this despite the current existence of a niche market for the smaller warmblood under 16hh; I’m talking about larger trends here.

** Am I the only one who thinks horses can actually measure differently on different days? Measure a horse you’ve just turned out on a cold winter’s day or just moved to a new environment, then measure that horse after he’s been napping on a hot summer day.

[CDE_Driver]

Purely anecdotal…

I bred my KWPN mare as a three year old. She was 16.2ish and substantial. Stallion is 16.1 and more refined.

First foal, filly, now three coming four. She is BIG. Substantial body, big feet, 17.2. Phenotype favors the dam.

Second foal (same cross) Gelding coming three. Much more refined and “pretty”. Most people think he’s the filly and she’s the colt. He is pushing 16 hands now. Phenotype favors the sire.

Oh, and the broodmare mare is now 17.3, she just kept growing and growing!

[grayarabpony]

[QUOTE=wyeoakequine;7331090]
Thanks for sharing your thoughts, all! I felt the article I shared had to be oversimplifying it to some degree. (I’ve kinda felt The Horse has been watering down their stuff more and more recently- I remember it being a much more “meaty” publication ten years or so ago.) Perfect example pointed out by arlosmine… the article suggests that the foal will inherit it’s phenotype from either mom or dad, but how would we get “frankenponies” if it were that simple? Surely, we know that some mixing of the phenotypes is typical.

As an aside, arlosmine, your Haffy cross sounds like a gem. I love the fact that you love him for who he is! Maybe that seems odd to say, but I spent too long working for a breeder who couldn’t see the virtue of anything outside her strange image of perfection. It was only a year, but it was TOO LONG!

Thanks for sharing that link, stoicfish! I went through to the actual study to get a little more info, as I was confused by what might be an error in the summary. It says both smaller and large warmbloods are homozygous for the mutation. Maybe I’m missing something, but wouldn’t it make more sense if large warmbloods were homozygous for not having the mutation? That’s what I got from sifting through the study.

In any case, it’s interesting that the heritability of height is documented stronger in ponies, though I’d think this would apply less to the sport ponies with warmblood in their background. I’d also wonder if similar heritability of height is seen in horses who are homozygous for NOT having the mutation- your super big horses. And with this model in mind, it makes sense why we see so much unpredictability when we breed horses of moderate size that are likely to be heterozygous.[/QUOTE]

The article is completely simplifying the genetics of height. It’s assuming there is ONE gene for it, and that one is dominant over the other. Genes can be codominant, affected by modifiers, etc.

The article is basically an opinion piece based on guesses that are very probably inaccurate.

[Erin_Pittman]

I have two mares that I have bred to different sires.

Mare #1 is a Trakehner/Morgan cross by Pregelstrand. She is about 15.1 hands. She had a foal by a 16.2-ish Hanoverian stallion (that wasn’t one of my foals) - that one was closer to the mare in height, being about 15.2/3. Foal #2 was mine, by Sempatico (16.1) and he finished out closer to Sempatico’s height at 16 hands. Foal #3 was by the Trakehner Hadrian (17 H) and he was 16.3 when we sold him at age 5.

Mare #2 is a 14.2 H pinto mare (her sire was a 15.2 H Paint). First foal was by a 17 H Thoroughbred stallion. I was told by the stallion owner that his foals tended to follow the dam’s size and that certainly proved true with this filly, who finished out at 15.1. Foal #2 is by our stallion, Salute The Truth - also a 17 H Thoroughbred. That gelding, now 3, is currently exactly 16 hands. We have noticed that offspring by STT tend to be bigger than their dams, though there are exceptions to the rule. We bred one gelding, out of a 17.1 H Trakehner mare, that is now 18.1 H!

[Fred]

I find the subject of heritability of height to be very interesting.
I have had the opportunity to see a number of members and subsequent generations of one family, and often wonder what actually determines the height.
My mare was 16.2. She was bred to a 15.3h TB stallion and produced a colt who matured to 17h. Following that she was bred to a 16h TB stallion and had a mare who was 16.h. Then I bred her to another 16.2 h TB and she had a colt who matured to a hair under 16.3 and a filly who matured to 16.2.
The 16 h daughter was bred 3xs to the same 16.3 Holsteiner stallion and her first colt matured to 17h, her second colt matured to 16.2, another filly matured to 16.1 and another daughter by a 16.3 h Holsteiner matured to 17h.
The 16.2h 1/2 sister had 3 foals and they all matured at close to 16.2.
So, the simple answer is that they are all within the 16-17 h range, but I have no idea what causes the range.

[stoicfish]

[QUOTE=grayarabpony;7332260]
The article is completely simplifying the genetics of height. It’s assuming there is ONE gene for it, and that one is dominant over the other. Genes can be codominant, affected by modifiers, etc.

The article is basically an opinion piece based on guesses that are very probably inaccurate.[/QUOTE]

No where in the article does it say that height is only based on one gene. It does however, try to give the average person an understanding of how genetics works and why the height of the parents is not necessarily the deciding factor.
It is correct information, it just does not have all the details that would probably not be helpful to most of the readers.
I bet there are a many genes that are responsible for the finished height, including the ones responsible for skeletal proportions, metabolic traits and a host of others.
On that level it is really complicated, yet on a practical level you can look to the pedigree and see what is present. Horses that are around 15 hands for the last 5 generations should hold no surprises. They are homogeneous for those traits.
However, Wb’s, like people pointed out, are not always recorded accurately and have a huge variation in size and type. I think Contendro is known for throwing some smaller and larger horses. His pedigree on the dam line has some smaller horses and the sire line has some very tall horses, apparently, he carries both traits that he can throw. http://www.sporthorse-data.com/d?i=10005018

[VirginiaBred]

@omare

Wow-I guess the pony people may have insight to that: how to explain the xx mare crossed with the welsh pony to get your large division pony if the dominant gene rules or does it?

@arlosmine

The hunter pony people most likely do a lot of research into the size behind the individuals to be bred, and even the pros get oversize larges. You just don’t hear about them.

My family has been breeding ponies since very early in the 1970’s. In the entire time (up to this year) that my mother and I have bred ponies, we have only had two go over 14.2. Both were bred to stay ponies!

I bang the pedigree drumb ALL THE TIME when people ask for my help in the selection of a stallion for their mare, (or vice versa). You absolutely must know what is behind your choice of stallion (or mare) in order to avoid the “bad sizes” and sometimes that won’t help (but very seldom).

Crossbreds of any type (Warmbloods, British Riding Ponies, German Riding Ponies, Welsh - TB cross or crossbred ponies where both sire and dam were both crossbred) are NEVER predictible.

Do your homework!!! Study what size get a stallion tends to sire and if the mare has had foals previously, learn what size she ended up having when all was said and done.