Sire Lines: Fact and Fantasy

[xfactor fan]

There's been enough activity on the Raise a Native topic on sire lines that a thread all by itself seems to be in order.

Please have patience with going over old ( and I'm sure that most of you guy know all this stuff) information. But I'd like to set the stage to insure that when the discussion starts, we are all arguing apples to apples and oranges to oranges.

By common understanding a sire line is the top line of the pedigree, tracking male descent. All modern TB's go back to three foundation stallions, so it could be said that the three sire lines are Darley, Godolphin, and Beyerley.

Modern usage counts more modern stallions, Mr. Prospector, Raise a Native, Man O'War, Native Dancer, Northern Dancer. And tends to leave out stallions between .

Northern Dancer could be said to belong to the Nearctic sireline, Bend Or, (or Tadcaster) Doncaster, Eclipse or Darley sirelines with equal accuracy.

There are two major points about this method of tracking descent.

This line follows the transmission of the Y chromosome. The only thing Northern Dancer is likely to have in common with Eclipse is the Y chromosome.

Modern genetic tells us that there is very little information on the equine Y . The only genes left are those that tell the developing embryo to be male not female. The equine X chromosome is huge and carries all manner of genes.
My guess is that any genes that were originally on the Y, now reside on the X. This process most likely took place way back in the dawn of time.

So there is no functional genetic advantage to having a Y from one sire line over another sire line.

So from the genetic standpoint the Y is interchangeable with any other Y.

That's what modern genetics has to say about the matter.

The other thing that the male line of descent has is the non-genetic information. In human terms sons of a father will carry the same last name. Mr Smith transmits his Y chromosome plus this non-genetic last name to his sons. In human families the non-genetic component includes: last name, social class, wealth, education, and parenting. Was Mr Smith a good parent? did he set up college educations for his children, was he a drug user? Did he father the children then walk away from his offspring?

In horses, where the modern TB stallion has very little interaction with the mares, much less his foals, the behavior patterns are not passed along. But the human interaction with the stallion is.

The top line of the pedigree has the greatest amount of human selection. Each modern stallion is the sum of hundreds of years of human interaction, human selection. This is also true of the female side of the pedigree but there is stronger selection pressure on the males. Most mares turn into broodmares. Only about 30% of colts are kept as stallions.

The Raise a Native may be a successful sire line not because that Y is better than other Y's, but because the human connections made a series of good choices. Starting with standing a stallion that only started 3 times. Raise a Native has some pretty impressive breeders in his background. Just to name a few in the first 5 generations, Hancock (imported Teddy) Vanderbilt (Discovery) Widener (Sickle) Whitney (Whisk Broom) and the list goes on.

What keeps a sire line strong is the luck to have capable humans managing the breeding not the genes on the Y chromosome.

[Bast]

What keeps a sire line strong is the luck to have capable humans managing the breeding not the genes on the Y chromosome.

And having suitable mares available.

When one line has been extemely successful--such as Sunday Silence in Japan--there may be a scarcity of mares of very high class for the sons and grandsons of Sunday Silence.

[louis finochio]

A successful stallion will breed tons of superior runners with mediocre mares. A non-successful stallion that is bred to those blue blood black-type mares will strike out.

[Bast]

A successful stallion will breed tons of superior runners with mediocre mares. A non-successful stallion that is bred to those blue blood black-type mares will strike out.

Louis, please, let's stick with science and standard industry terms and measures, not what you make up.

I've never heard a successful stallion defined as you have. In the first place, it is subjective. What is mediocre? What is a "superior" runner?

You have a thread in which you are allowed to post your "theory" and in which you are protected to do as you please. Revel in that.

[louis finochio]

I didnt make up, superior runner, medicore, or non-successful stallion. I inherited them from those who have gone on to greener pastures. RIP my friends.

[Bast]

I didnt make up, superior runner, medicore, or non-successful stallion. I inherited them from those who have gone on to greener pastures. RIP my friends.

Okay. May as well give up on this thread as well since it has gone off into fantasy.

[Toccet02]

So, my first thought is that there MUST be at least superficial info that the males pass on...what about all those farm websites that advocate crossing a sire with a particular body-type mare in order to produce a certain body type in the offspring? You're not saying that the ONLY trait a male passes on is whether or not to be male . . . or are you?

[Bast]

So, my first thought is that there MUST be at least superficial info that the males pass on...what about all those farm websites that advocate crossing a sire with a particular body-type mare in order to produce a certain body type in the offspring? You're not saying that the ONLY trait a male passes on is whether or not to be male . . . or are you?

I certainly am not.

[brogers]

So from the genetic standpoint the Y is interchangeable with any other Y.

While we (Pedigree Consultants) are as guilty as any in talking about sire lines as if they exist, the more you look into it, the less appealing the concept is. It is popular (the concept of a sireline), but so is the X-factor, and both aren't based on scientific reality especially if you limit the concept of a sire line to just the Y Chromosome.

My only addition to this would be that recent literature suggests that in eukaryotic systems the methylation pattern in sperm can be linked to epigenetic control of the developing embryo. Stated another way, the chemical modification in the DNA (that is all DNA not just the Y) that will be passed from the sperm to the egg will actually control the gene expression in the developing embryo. This is a method of genetic imprinting and can have significant affect on the development of the offspring and may be a fundamental difference between successful and unsuccessful stallions.

[xfactor fan]

brogers,

Is there any research that says the changes in the sperm itself are inherited via the male line? Or only via the male line?

Epigenetic is a whole new can of worms, that may stand Mendelian genetics on its head.


Just for the record, I'm not ignoring the rest of the chromosomes and genes that a stallion passes on to the foal. Just saying that the genetic basis of a sire line is more fantasy or wishful thinking than fact.

[brogers]

brogers,

Is there any research that says the changes in the sperm itself are inherited via the male line? Or only via the male line?

Xfactor

I haven't seen any research to say either way. It would be a real find to know if methylation patterns in sperm were in some way heritable as it would explain some type of "sire of sires" effect.

As it stands with current knowledge, and I there are others that know more about this than me, I believe that each stallion should be treated as a stand alone opportunity as far as success/failure at stud. I guess Sadler's Wells/Tate Gallery/Fairy King, Devil's Bag/Saint Ballado, Vice Regent/Viceregal, Pharos/Fairway, His Majesty/Graustark, have shown us that already.

The main reason I mention methylation patterns and its effect on epigenetic control of embryos is that there is statistical evidence that a stallion first breeding/cover (usually in the morning) is slightly more likely, just slightly, to provide a stakes winner than subsequent breeding/covers, and that breedings/covers that occur in certain months are again, on a statistical basis more likely to produce stakes winners than other months. Also, the DNA doesn't change over time in a stallion, but the methylation pattern can. This would explain in some way why stallions have lesser production of stakes winners as they age.

[Tappiano]

As a stallion ages is he more likely to cover younger, unproven mares or proven ones? Females are born with all the eggs they will ever have and in the human population research suggests that older eggs might have some "issues" with them. Since sperm that are produced are new throughout a stallions life, it could also be said that environmental factors would have some kind of influence as the conditions that are present when these new cells are created are different each day.

[xfactor fan]

Any data on time of cover for the mares? Or just human selection?

The guy is scheduled to jump three mares, and the humans bring him the best mare of the three first?

In some animals sex selection is influenced by how early in the heat cycle the female mates. The logic is that early in the season means that there are lots of males around, so females are produced, late, not many males so more males.

Could this be an effect from the dam, and her cycle?

[brogers]

Time of cover was looked at I believe. It was a European study so I am thinking it might be interesting to see if it is repeatable with North American data. I don't think that there was any sex bias in terms of when the foals were born but I will have to dig the study up to confirm.