Line Breeding & the X-Factor

The Large Heart Characteristic

Articles & Information For 'YOR' consideration in equine breeding.

How to calculate the percentage of genetic influence in a horse.

"If a horse inherits more intelligence via the X-chromosome, and a breeder is selecting for this gene, doesn't it stand to reason that a Western Pleasure, or Cutting or Reining horse has much to gain by inheriting a superior X-chromosome?" - Andrea Laycock Mattson - Read the article HERE.

Simply put, the X-chromosome (female) is larger than the Y-chromosome. It carries "more" genetic information forward... perhaps intelligence, but certainly the "large heart characteristic"... the X-Factor.

TB Line-breeding Comments from Roy Brewer of Hammersmith Hill:

So how do we upgrade our mare(s)? Well I have spent the last ten years or so researching the idea and I will share with you some of my thoughts.

I have looked at most, if not all, of the great racehorses of the 19th and 20th century. I have studied the produce of the greatest breeders of all time, looking for patterns that would fit today's racehorse, and I have come to some interesting conclusions. First, unless you have a horribly inbred mare, out crossing (no common ancestor in the first five generations) is not the way to go.

Also, inbreeding and/or line breeding to just the male line of a pedigree or breeding a sire line to a broodmare sire line is not very productive. I should note that when a 'nick' occurs between a sire and a broodmare sire it is usually because the stallion's tail female line has a number of identical ancestors as the mares tail mail line.

So let the experts tell you what they want, but according to my research the best breeders have constantly line bred and occasionally inbred their mares to stallions whose pedigrees were filled with a number of identical ancestors as their mares. Let me qualify this by saying that they crossed their mares with stallions that had an abundance of top quality racehorses in their pedigree.

Also, their results got better when they crossed the gender line of particular horses (sons and daughters, or full brothers and sisters 3, 4, 5 and 6 generations back in the pedigree). Frederico Tesio, the perennial leading breeder of Europe for fifty years did this all the time and he bred three undefeated champions including Nearco and Ribot and Donatello II. The list of champions that are bred this way is endless and our list of local champions fit the same mold.

So what's working right now? Well there are some distinct commonalities that I have been witnessing over the last 2 to 3 years, whether they are global or here in our backyard.

1) First and foremost, inbreeding and/or line breeding to Northern Dancer is, without a doubt the ticket! From my observations, this is the most productive pattern in stakes horses in the last three years. I have seen multiple crosses (2, 3 and 4 times) of Northern Dancer in at least 25% of the graded stakes horses that I have researched over the last three years.

The richest filly of all time (Spain) is a perfect example. Also, seven of the 21 top three finishers in the 2002 Breeder's Cup had this trait and the top four finishers of this year's Irish Derby all carried this trait (the top three finishers all by Sadler's Wells and the fourth place finisher a grandson of Sadler's Wells).

2) Two names that are being line bred on a constant basis are Nasrullah and Native Dancer. I have seen Nasrullah as many times as eleven in the first six generations of a pedigree and Native Dancer as many times as five in the stakes horses I have researched. Basket Weave, Slewdledo and Tough Knight all have been very productive with mares that have multiple sons and/or daughters of Nasrullah in their pedigree.

3) The cross of Seattle Slew and Mr. Prospector or Mr. Prospector and Seattle Slew. Top or bottom, it doesn't seem to matter, there have been numerous successes using this cross.

4) A couple of other productive crosses to consider are: Northern Dancer / Native Dancer, or Mr. Prospector / Fleet Nasrullah.

I know that there are other considerations when choosing a stallion for your mare, such as conformation, size, temperament, etc., But given those considerations, if you concentrate on breeding your mare to proven stallions or to new stallions that meet the above criteria and that when crossed show line breeding and/or inbreeding that links together in the first five or six generations some of the greater racehorses through both sexes, I believe your chance for success will improve greatly.

Roy Brewer

The old saying goes that "you don't know if you have a great stallion until you line-breed with him". The general premise is that you magnify the good traits. You also magnify the bad traits, so if there are very few or none of those, you have a good result.

Intense line-breeding must be followed by an out-cross.

To date, we have crossed High Noon back on his own daughters a number of times - all with excellent results. We have also crossed half siblings with great results.

Click HERE to read an excellent article on Breeding Selection and effects of Line Breeding (especially as related to Peruvian Horses). Use your BACK button to return to this page.

Click HERE to read an article about HYPP - the dark side of line-breeding that can perpetuate genetic defects. Use your BACK button to return to this page.

The AQHA stallion Royal King is credited with an X-Factor that brings incredible performance capabilities forward through his daughters. Read this article about the Smart Little Lena X-Factor from Royal King - in noted horses like Royal Blue Boon, etc. in the Cutting, Reining & Cowhorse world.

If you look back, Royal King is line-bred on a TB mare named Barbee Dun - who traces back to Glencoe, line-bred on Eclipse.

 

The X-Factor refers to the X-chromosome, carried forward by the female line. Males have an X chromosome, which they receive from their dams and pass to their daughters, and a Y chromosome, which they inherit from their sires and pass to their sons. The Y chromosome is much smaller than the X chromosome and carries less inheritable material. It is basically a sex determinant and when thrown into the mix at the moment of creation makes that individual a male. If the sire contributes an X chromosome, then the resulting foal is a female. The Large Heart Characteristic Because the large heart characteristic is on the X chromosome, large-hearted stallions that carry only one X chromosome, which they receive from their dam, can only pass on the large-hearted X chromosome. In the case of their daughters, they carry their sire’s X chromosome and one of the two X chromosomes carried by their dam. Whichever X chromosome is dominant is the one that is expressed. If a mare is a single copy (meaning she carries the large heart on only one of her X chromosome), she could pass on either the large-hearted X chromosome or the small-hearted X chromosome. Depending upon whichever X chromosome is dominant, that mare might express either a large heart or a small heart.is a female. Click HERE to read a fasinating article on the Large Heart & X-Factor tracing back to the legendary TB "Eclipse". YOR High Noon traces back to Eclipse through his mother S/W Red Velvet - from her TB bottom side.... and through the Mansfield Comanche line-bred top-side of his pedigree. YOR All Heart CJ - grand daughter of Tiny Charger - one of our leading broodmares - traces to "Eclipse" through 8 different lines. No wonder she is special. YOR High Noon X YOR All Heart CJ have already produced World Champion (in Reining) offspring.

Foundation AQHA stallion Peter McCue is interestingly out of a mare that was line-bred on Glencoe (a line bred stallion going back to Eclipse).

Why does the Large Heart Characteristic matter ? It has been proven that the heart size of an athlete can enhance performance.
In Australia, they did a retrospective study of Thoroughbreds. The conclusion of this study came to an astounding figure. They found that 89% of high-class winners had large heart scores. Compare this to the general population where only 25% of horses have large heart scores, the results are very exiting indeed!!
One must remember, however, that the heart size of a horse can only provide results if other factors are in play. Research has concluded that 22-23% of a horse's ability comes from it's heart score. This means that approximately 77% comes from other factors. These could be conformation, training techniques, feed, disposition, and numerous other factors in a horses day to day routine. One must always remember and give credit to the human intervention and influence to a horses performance.

 

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