X factor theory

[sbcaris]

Turningforhome: Can you shed some light on the X factor theory. People on the pedigree query site say that the X factor theory has been proven wrong since they have never found any genes on the X chromosome related to heart size, shape etc.

Are they right in this regard? What is your take on the X chromosome being very important to thoroughbreds?

[turninforhome10]

Just let me say this, while the large heart theory can be debated till the cows come home, the data that the Big 4, Mahmoud, War Admiral, Blue Larkspur and Princequillo have produced in the classic races have been undeniable. My personal theory makes that the large heart was a mutation. Maybe from Eclipse but certainly through Pocahontas.Citations
Sometimes I feel more like because these lines were said to have been the best, they became sought after thereby raising the bar of those who would be made available to the line. Maybe it was the best to the best that helped make these lines thrive. It is a fact that Secretariat had a huge heart with no myopathy. So if Big Red's mom could pass this one to him, it is proof that it exist's and most likely it maternal mtDna that is responsible for it. Maternal MtDNA is slow to change and can be used to trace the allele responsible. The Irish are way ahead of us on Equine research. There are also Speed Genes and now also talk of Gate Keeper Gene
If the pedigree people think that it a debunked myth, how do they explain the impact the Big 4 have had on classic races?

[turninforhome10]

Thinking about it, it would make a good topic for Freakeconomics. Is it nature vs nurture? Is it economic? Is it that the some of the best mares are owned by some of the most economically advantaged people? Would make a good paper.

[sbcaris]

Turninforhome10: You said that since Secretariat's dam could pass that heart on to him it proves that it exists. I assume that you believe the large heart gene was transmitted from Somethingroyal to Secretariat by way of her X chromosome. Unfortunately,--------

There has never been any genes discovered on the X chromosome that have anything to do with heart size or function. To date there is no such thing as a specific large heart gene. No such gene has ever been recognized by Genomic scientists throughout the world.

However, I do believe in the X chromosome as being a very important influence that is a major part of why some broodmare sires are great filly sires: Buckpasser, Sir Gallahad III, Princequillo, Blue Larkspur, Mahmoud, War Admiral etc. The X chromosome is 2/3 larger than the Y chromosome and therefore carries much more genetic information.

Interestingly, a colt gets more DNA from his dam than he does from his sire. He gets an X from his dam which carries more DNA than does the Y chromosome. Furthermore, any traits carried on the X will be expressed because the Y chromosome does not have any homologous genes to suppress those on the X. (except for a few genes that are found on both the X and y which are homologous)

I do believe that having Buckpasser in the X is a major role player in the success of many outstanding thoroughbreds.

[turninforhome10]

No gene has been found on the x gene by itself. It is a combination of genes that allow for powerhouse mitochondria to fuel the cells themselves. I don't think it is really fair to even call it a large heart gene based on this citation .

"Even though there was an Australian study in 1977 that found a correlation between heart scores and performance, later studies did not support that hypothesis. Most genetic studies on horses are also using data from the Horse Genome Project at the University of Kentucky in their research. If a genetic link exists then using that data often (but not always) leads to a scientific link being found quickly. Several scientists have began to investigate the x-factor theory but has since abandoned their studies. Although not conclusive, this indicates to skeptics that no clear x-factor link was found using the Horse Genome Project data.

Some have also pointed out that heart size can change in association with pathology and that large heart size is sometimes a sign of heart problems, hence a large heart is not always a good thing and not always inherited by genes.

Several extensive equine genetic studies have located genes related to heart size on autosomal (autosomal are non-X and non-Y) chromosomes, but have not located any such genes on the X chromosome alone, which some critics have interpreted as disproving the whole x-factor theory altogether.

The explanation of how poor sires can be great broodmare sires, especially Secretariat, has also met with much criticism. The criticism is that while Secretariat has become a great broodmare sire that is not because of him but rather because he was bred to many of the best broodmares from all the best maternal families. Secretariat was a much better broodmare sire not because he is an x-factor carrier but because his daughters come from some of the best and finest maternal lines around and this is the primary reason. Secretariat is just benefitting from being mated to some of the finest broodmares at the time and it is their maternal families that shine.

Finally, some have criticized the theory for its oversimplification. How can racing performance primarily be a factor of one gene pair when the horse consists of a lot of different genes?


I believe that all things are to be considered. Can a horse with large heart run well if he is unable to maintain a high cruising speed because of confirmation? Can they mature properly without proper nutrition? Can they achieve their best without proper training?
One thing can be said about Buckpasser mares, they were the best producers so they would have been owned by the top end of the market. Look at some of the ownership names on them. It is a who's who of the old breeding titans.
So while I agree that Buckpasser in the X is big plus. Is it really even genetics for the reason?

[sbcaris]

You said Buckpasser in the X is a big plus, but is it even genetics for the reason?

Of course it is due to genetic traits carried on Buckpasser's X chromosome which he got from the outstanding broodmare, Busanda, who beat the boys going long in major stakes. That X that Busanda gave Buckpasser carried many genes for above average performance which allowed Buckpasser to become the leading Broodmare sire 4 times.

Buckpasser has been identified as a Classic chef de race and one can induce that on his X chromosome are many genes that may contribute to that classification.

Here is a very interesting piece of data concerning Buckpasser in the X compared to Mr. Prospector in the X (both of whom were outstanding broodmare sires).

Buckpasser is found in the X passing position of 7 Kentucky Derby winners and 8 place finishers.

Mr. Prospector is found in the X passing position of ONLY 1 Ky Derby winner, Super Saver and 2 place finishers.

In the Belmont stakes Buckpasser is found in the X passing position of 9 winners. Mr. Prospector in the X passing position is found in Zero winners of the Belmont stakes.

In the Preakness 6 winners have Buckpasser in the X. Not a single winner has Mr. Prospector in the X.

Conclusion: There may be genetic traits on Buckpasser's X that spell stamina. Mr. Prospector's X chromosome has very little stamina genes on his X or one would expect much different results in the Triple Crown events. Mr. Prospector led the Broodmare sire list around 9 times but as far as the Triple Crown is concerned he has had little influence from the X bearing positions.

[turninforhome10]

I understand that you are trying to drive home a point about Buckpasser and his data is solid, but(from my 2012 column).....
"
"38 winners of 57 Derbys since 1954 well over 50% just from 3 broodmare lines. Direct female descendants back to War Admiral, Mahmoud, Blue Larkspur foundation mares through tail female".
Add I'll Have Another ( Mahmoud tail female)
American Pharoah (Mahmoud)
So was it Buckpasser or was it that Busanda carried War Admiral and Blue Larkspur and was from the holy grail of female lines. And we will make that number 40 winners from 62 Derby's.

[sbcaris]

Turningforhome10: Interestingly, 18 of the 20 horses in last years Ky Derby had one of those 3 major stallions in the X passing position: War Admiral, Mahmoud or Blue Larkspur.

And 90% of the starters is just way too high to be used as any meaningful handicapping factor.

Your statement that 40 of the last 62 Ky Derby winners carried one of those three stallions in the X passing position cannot really be used in any meaningful way by itself because around 90% of all horses in the Derby carry at least one of the above stallions in the X position

[turninforhome10]

Not x passing position. I am talking the tail female. A female directly on the bottom of the pedigree(mtDNA). This would mean that Buckpasser traces in female lineage by way of War Admiral x Blue Larkspur x Teddy(Exceptional brood mare sire) X Helicon X......back to etc. I don't know if we are talking about the same thing?

[dilanesp]

It's worth noting that the 22lb heart story for Secretariat is almost certainly a fish tale. He was x-rayed and had a large heart, but not anywhere near 22 lbs. The 22 pound story was never documented- it was a statement by the physician who did the autopsy, but there were no photos, no autopsy report, etc. He also claimed Sham had the second biggest heart in history, which is preposterous.

This whole area is one where extreme skepticism is warranted.

[PowerUpPaynter]

what is the tail female? Is that the very bottom of the pedigree that passes all thru female to female?

Like for example lets say we use fact finding (http://www.pedigreequery.com/fact+finding2)

Is that Buckpasser considered in the "tail female"?

and are you considering the X position anything passed from the dam side?

[turninforhome10]

Originally Posted by PowerUpPaynter

what is the tail female? Is that the very bottom of the pedigree that passes all thru female to female?

Like for example lets say we use fact finding (http://www.pedigreequery.com/fact+finding2)

Is that Buckpasser considered in the "tail female"?

and are you considering the X position anything passed from the dam side?

The tail female is the very bottom of the pedigree. In Fact Finding, Buckpasser is in the tail female through Glisk. This tail female line has a number. These numbers, while antiquated for some, allow for classification. For example if you see a horse like Fact Finding and see Family 1-x you learn to know that is La Troienne and in this case through Big Hurry( Pure Col Bradley Blood lines).
For the purposes of data collection, I am only considering horses on the direct female line, nothing in the x passing position.
For my own purposes, I like to see inbreeding through great females. Take the burgeoning Ap Indy\ Storm Cat cross. I love putting Terlingua and Weekend Surprise back together in a pedigree.
So while having Buck in the x passing position is beneficial, having the right females on your tail line is 40 of 62.

[sbcaris]

Turningforhome10: OK, your stat of 40 of 62 comes out to around 66% winners of the roses trace in tail female to one of the big 3 stallions. The only way you can decipher if this is a good method is to compare the starters in the Ky Derby who qualified on this direct female line to War Admiral, Mahmoud, or Blue Larkspur.

For example: If 66% of the starters in the Derby also trace to one of the big 3 stallions in tail female, then your 40 of 62 statistic carries no clout at all. If on the other hand only 33% of the starters trace to one of these stallions then you are on to something that carries signficance. Then the impact value would be 2.00 which means these horses are winning the roses two times more often than expected.

Did you ever collect any data regarding the percentage of starters in the Derby that qualified on that direct line angle of yours?

[turninforhome10]

Originally Posted by sbcaris

Turningforhome10: OK, your stat of 40 of 62 comes out to around 66% winners of the roses trace in tail female to one of the big 3 stallions. The only way you can decipher if this is a good method is to compare the starters in the Ky Derby who qualified on this direct female line to War Admiral, Mahmoud, or Blue Larkspur.

For example: If 66% of the starters in the Derby also trace to one of the big 3 stallions in tail female, then your 40 of 62 statistic carries no clout at all. If on the other hand only 33% of the starters trace to one of these stallions then you are on to something that carries signficance. Then the impact value would be 2.00 which means these horses are winning the roses two times more often than expected.

Did you ever collect any data regarding the percentage of starters in the Derby that qualified on that direct line angle of yours?

I have done my own research regarding top stallion and broodmare lines from Derbies past, but a study such as that would require some time. I have the program to do it but no one would be willing to pay for such a study. To be honest I fell into the data by accident while compiling information on Triple Crown winners. It is just a personal angle of mine that has worked pretty well to find horses bred on classic lines. Am I trying to prove that it will work to predict a Derby winner, never confessed to anything of the sort. More of a neat fact without further study.

[sbcaris]

Turningforhome: The problem for the handicapper is as follows: Since the vast majority of Derby starters qualify by tracing in tail female to one of the big 3 stallions (War Admiral, Mahmoud, or Blue Larkspur)along the tail female line, the angle by itself carries no clout for the bettor.

My angle on Buckpasser in the X by itself is no good without adding some other factor to it (Buckpasser in the X plus a fast finish at 9 furlongs).