Pedigree Generation Position

Inbreeding/Line-breeding and its Statistically Beneficial Generation Location

In our quest to breed sport horses with potency for excellence in sport, we want to find the most favorable pedigree generation position for building potency. Most of us have been told by the authorities that only the first three generations of a horse's pedigree is significant. They will usually state also that the genetics of any individual horse further back is too slight to be of any importance. And the reasoning does seem logical when you look at the following percentages:

1st generation- 50%, 2nd generation - 25%, 3rd generation - 12.5%, 4th generation - 6.25%, 5th generation - 3.125%, 6th generation - 1.56%, 7th generation - .78%, 8th generation - .39%, 9th generation - .195%, 10th generation - .01%

The line-breeder's response to this apparent fact is this: We agree that the percentage of influence of an individual ancestor that will carry forward to the foal can be gauged as the above shows. However, if you add multiples of an ancestor into a foal and close relations such as full and part siblings, you have not only added these percentage amounts, but also multiplied their genetic influence by expanding the entire presence of common genes and their quality--and created a dominance--and it is dominance that sets type.

In order to set the type of sport excellence we desire in our horses we must increase the genes that carry those traits, and this is accomplished by inbreeding or line-breeding. But all individual talented ancestors are not equal, you can have a top performer will little potency, and so we look for superior ancestors to increase that are already potent themselves.

"...some names because of their own concentrated genetic background appear in practice to exert a far greater penetrative strength for their genes than others." (Clive Harper)

This is a key point, that it is not just inbreeding or line-breeding, but the quality of the duplicated ancestor that will make a difference. So we should be asking, does the ancestor we want to duplicate possess a powerful genetic package already? And we should not just look at the performance record, a horse can be a performance star like the magnificent Ratina Z but not be genetically powerful enough to reproduce her own level of talent consistently. It is interesting to our study that Ratina Z was bred to her full brother --therefore doubling the genetics (extreme inbreeding 1x1) and the result was the stallion Rex Z. Was he a world beater like her? No, he had the best training and management possible, yet was  only a moderate jumper, and his stallion record, even with access to the best mares of the Zangersheide Stud is average also, with just one great offspring and she, Regina Z is out of a powerfully bred trotter, who is 86% American Standardbred--a breed not even allowed in their Z registry (read more about this fascinating episode in Standardbred Sport Horses.)

It was the powerfully bred trotter lines that gave Regina Z her above average talent, not the loosely bred Holstein half. Her dam is inbred 3x4 to the incredibly potent Stars Pride ST, who is himself inbred 2x2 to full brothers: Mr. McElwyn ST/ Warwell Worthy ST, who themselves are 3x4 to the full brothers Guy Wilkes ST/William L AT (ST=Standardbred, AT=American Trotter)--this is potency of the highest quality. In contrast, Ratina's nearest potency is a double of Loretto HO and Favorit HO 5x5. Quite a different picture, you can see how much looser the breeding is from the pedigree which has the duplications highlighted. But there is something else seldom considered, Favorit HO and Loretto HO are old style coach stock descended from mostly Yorkshire Coach Horses, where as Stars Pride ST is of course a racehorse--that is, a sport horse, with hundreds of years of performance testing behind him, therefore much more valuable than the coach genes for sport, and with tremendous potency in jumper lines (see Standardbred Sport Horses for the results of tracing back the jumper trait to its root).

The whole purpose of inbreeding and line-breeding is to set type and talent into our stock. We locate a ancestor in the lineage that is exceptional in the abilities, soundness and athleticism that we desire and we aim to make those genetics dominant.

In addition to the simple transfer of genes, it has been noted that genes travel in clusters. If all the genes in the cluster are positive this can result in a huge upgrading in prepotence for superior traits, far out of proportion to the simple percentage numbers listed above and this is why, when practicing line-breeding, it is imperative to choose superior ancestors to double up on. The augmentation is great with this type of breeding, and if inferior targets are used, then the downgrading can be massive also.

In 2003 I was still breeding European, and I was planning a mating based on a ancestor duplication for the 4th generation of the foal's pedigree. The wisdom of this was questioned by one of the heads of an American branch of a European registry; he said: " should think about going back to the fourth generation as an argument for your choice. There is almost no genetic influence anymore from bloodlines that far back." This opinion as I noted in the start of this page is the prevailing thought in the industry, and if you are a sport horse breeder you have probably heard similar statements.

Thoroughbred expert Ken McLean had these strong words for this same attitude in the Thoroughbred industry: "Certain people in the industry will say that it doesn't matter once you look beyond a three-generation pedigree. Let me state categorically, these people are downright ignorant!...A pedigree is a truthful blueprint of the animal's ancestry."

When practicing line-breeding, what generation position of the pedigree is most effective? Almost all horses, bad performers as well as good, are line-bred in some way. However, the extensive research that has been done into successful horses has shown that certain areas of the pedigree have proved more beneficial for line-breeding than others.

Edwin Anthony, Thoroughbred pedigree expert said " is not the fact that inbreeding or linebreeding is present, but how it occurs is paramount."

Before we continue let me warn you not to become legalistic about position placement. If you can step back from the pedigree you are trying to construct and become fluid in applying the breeding principles you will find it easier to create that special horse. Remember, we are usually not dealing with pure-bred horses when we breed sport horses, so we will have a harder time getting some of the recommended pedigree patterns. The pedigree equilibrium as a whole is the key, with sex-balanced line-breeding, full and 3/4 siblings, with both sides of the pedigree involved, and duplications through as many different siblings as possible.

In general the experts have determined that the focal line-breeding should be in what many call the engine room, which is the  4th through 6th generation positions. Here are a few of their opinions:

The Lesh brothers, early evaluators of Thoroughbred pedigrees, determined that the 3x3 position has only a slightly higher percentage of winners than average, but a very high percentage of good producers. Later researchers have agreed with this finding saying that inbred horses are often extraordinary producers.

David Dink, who entered his research to disprove the benefits of linebreeding, ended up reporting that he found duplications of significant ancestors in the 4x4 position best for winners.

Harold Hampton, who alerted the Thoroughbred breeders "down under" to the benefits of balanced linebreeding, believed the 5x5 position was premier.

Clive Harper, who gathered the results of the previous pioneers to give us a detailed overview, said that better horses have more line-breeding in the 4th, 5th and 6th, and they also need an instance of 3/4 or full siblings within 6 generations.

Harper's research went much farther into this. He also saw that the best horses accumulated multiple lines of an important mare or sire in the far reaches of the pedigree, and had reinforcement for that presence in the engine room area. And of that target ancestor in the far reaches (7th to 14th generation) he rated them as such: good- a tap root mare; better- a pair of full sisters; best- a full brother and sister.

When he was asked what he considered the perfect pedigree, he said that would be 4x4 to a full brother and sister, with each having reinforcement to its ancestors. He particularly liked to see one side of the pedigree develop the dam ancestors of the full siblings and the other side to develop the sire side ancestors. He said the closest he ever saw of his ideal pedigree was in the Thoroughbred Fair Trial

Just recently the Thoroughbred pedigree expert and creator of  PedigreePost, Les Brinsfield, sent many of us the pedigree of Sweet Loretta, a daughter of the great Tapit, and said he thought it was the best lineage he ever saw. Compare these two pedigree designs with that of Ratina Z in Regina Z pedigree and you will see once again the lack of potency in Ratina Z. Often performance stars can have loose lineages, they just became lucky in the phenotype when the genes divided they got the better sport half there, but their genotype doesn't reinforce the talent enough to make them top breeding stock.

Pedigree theory is complex, but it is worth pursuing. I suggest that you start your program with baby steps, like sex-balancing an important line for your goals that is sitting in the "engine room" (4th to 6th generation). Make that your target, and when choosing from mates that have this desired compliment, then look at how else they interact with your mare/stallion pedigree. And pick the mate that overall gives you the most dynamic combination. But focus on the target ancestor first--otherwise the sheer mass of pedigree names might overwhelm you.

How much line-breeding is too much? Can you overdue it? Probably, but if you balance the duplications and use superior ancestors as targets, then you will not lose hybrid vigor. Inbreeding or line-breeding to male only representatives of good lines is what is shown to cause loss of hybrid vigor. Take a look at the intense pedigree of the top Standardbred racer and stallion Muscle Hill, and you will realize if duplications are done with superior bloodlines it is hard to do 'too much'.

Be fluid in your pedigree design. If the most dynamic combination you find has a 3x6 duplication, then go for it. When the duplications are 4x4 or 5x5 they are equal in strength, but the reality in mates is not often so clear cut. For instance, the super mare Pocahontas, has her strongest duplication 3x5, her next three strongest are 5x7, 5x6 and 5x6. And she is considered one of the greatest mares ever, even 170 years after her birth. Try to keep the strongest activity in the "engine room" area and involve both sides of the pedigree, and you will do well.

For further depth of understanding in this practice, and the points covered in the other articles, I highly recommend that you investigate some of the writings by the pedigree experts, which you will find listed on the Resources and References page They did all the hard work for us. We have only to study it and then apply it to our own breeding programs.

A word about inbreeding for sport horse breeders: inbreeding is attempted by breeders when they want to create greater potency of a particular type into their herd. The most successful typesetters or 'improvers' in horse breeding are inevitably inbred. It is the fact of their inbreeding that allows them to transfer the potency in the traits that are desired. Most breeds have originated with inbreeding, because it will give a reproducible phenotype quickly. There is a common misconception that inbreeding causes defects or mutations. This is not true, what inbreeding does is concentrate the genetics that are present, so if the individual line chosen for the inbreeding has faults or weaknesses, you will concentrate them into the gene pool along with the sport abilities that were the goal. So I suggest that you do your research before you attempt it. When it succeeds you have set the type and sport ability into your herd- when it fails you have brought negative recessive genes to the fore.

What about outcrossing or cross-breeding? Outcrossing or cross-breeding can be the right choice for a breeder when they have built up their gene pool and want to bring in something new. We recommend that the individuals chosen for the outcross be of a similiar type for the sake of soundness. And that the respective pedigrees are close in genetic strength. If you chose an individual without strong linebreeding for the cross, you will not get the traits you wanted consistently in your foals. And you will actually be taking a step back for the sport talent. If you choose an individual that has a similiar genetic strength as your horses, but with the different lines that you desire, then you should have success for you will bring in hybrid vigor and add to your potency for sport.

For more compreheive instruction in Tesio Methods and the bloodlines that are top sport transmitters see: North American Sport Horse Breeder

Key Elements in Potency Building

Pedigree Study

Sex Balance


The Mare

Understanding Pedigrees