As is evident when grasping basic genetics, it is impossible to precisely calculate the actual amount of influence the blood crossed into a breed has on any individual horse once you are past the original 50:50 partbred. In the recent past this has served to denigrate calculating the infusion of English Thoroughbred into the Akhal Teke population.
Well, guys and girls, you can't have your cake and also eat it!
From scientifically well-accepted COI and relationship calculation up to (accepted by all of the breeders) simple studbook management (not just among Akhal Teke), basic percentage calculation is applied for practical reasons. It is not voodoo or amateurishness, it is being done like that even by professional geneticists up to the day.
Of course, the actual distribution of genes from one (mixed) parent or the other (mixed) parent to the offspring ought to be seen more like that of a bell-curve of probability, than linear.
However, it is wise to remember, that this curve goes both directions, meaning that implying that the influence lessens, because it is possible that less foreign (to the Akhal Teke) genes are traded, is a nice example for not so well-meaning window dressing. Does anyone truly believe, that just because genes are traded by Akhal Teke, that they do not make use of the full Mendelian spread? This hopeful, but really naive idea and argument misses out on another extremely important factor at work among this breed with regard to the Thoroughbred outcross.
Ever since the outcross the gene pool has been under a severe selection which actually favors the infused genes as opposed to the Akhal Teke ones! Under this type of selection a linear calculation can be regarded being an actually conservative method.
The alert observer can easily trace the combined result of outcross to English Thoroughbreds and selection for their main traits within the gene pool, which more often than not make it perfectly clear that the infusion was not lessened by time, it was being successfully selected for and fixed in the gene pool. It is obvious e.g. in lines Peren and Arab-Absent, just as it is obvious in line Sere.
919 Sere (3,9%) is a son of the pure AT sire 579 Sinok out of the impure mare 1195 Enish (7,81%), who trades English blood on both her lines, repeatedly so as well. Sere had the sons 1029 Antshar (1,95%) out of pure 1408 Agawa, 1107 Tshakan (1,95%) out of pure 1469 Guldshakhan and 1099 Serasker (3,02%) out of impure 1652 Sayat (2,15%). Sayat also traces several times to English blood in her back pedigree.
Both Serasker and Tshakan stood at stud at Stavropol, Antshar at the statefarm in Dagestan, but Kalmykian Chagorta also used him quite a bit.
Physically Antshar and Tshakan show a distinct old-style warhorse type. Even under the heavy feeding regime of Stavropol Tshakan was impressively dry, flat-muscled and harsh looking, the same goes for Antshar in Dagestan. Both had easy, light and fluid movements and there really was no mistaking either of them for anything but Akhal Teke.
Serasker on the other hand looked bloated, with bulging, undefined muscles and an enormous weight on him, weight which appeared to be mostly fat and very loose tissues. Where both Tshakan and Antshar show typical Akhal Teke conformation, relatively coarse profiles and lots of bone, Serasker - once you disregard the metallic sheen - could easily be slipped into a herd of Hispanos and not be discerned from them even at a second glance. His gaits were high and powerful (as in a lot of energy is being used for movement). Of the three stallions he was the tallest (1,64m) and he had an enormous, broad chest on him.
It is interesting to have a look at how these three sires were used and what kind of offspring they produced.
Chagorta and Dagestan, at the time still making relatively independent - from champion breeding - decisions, used Antshar heavily. His offspring was exactly in his type, a bit coarse in the head, flatmuscled and very dry, but what truly raised them above the average were their phantastically smooth and easy gaits. This traded so dominantly, that it was possible to look at a moving herd and pick out his get by movement alone. All of them had this "Sapar Chan air" about them. These horses also proved to be hardy and fast on the racetrack, especially in longer races. In Dagestan several Antshar foals were successfully trained and ridden in endurance races. As a whole, whether in private ownership or the statefarms, his get stayed mediumsized.
Tshakan on the other hand was soon discarded by Stavropol as a sire, for "not trading enough type" as per Stavropol's preferred type (see discussion on type in the selection section). It is quite clear that with his great similarity to Antshar in old-style looks, he traded them just as strongly.
The stallion staying in Stavropol and siring lots of offspring was tall hispano-warmbloody looking Serasker. His get is somewhat diverse, though as a whole also very tall (often with mares attaining more than 1,60m), heavy and high in movement. All of them tend to fatten up easily, quite a few seem to have loose tissues. Also quite a few apparently have health issues and are not that easy to handle.
Now, sheer percentage only tells you that Serasker has slightly more Thoroughbred infusion than the other two sires. The big "but" here being, that the way he looks, moves and trades do find their expression if you have a close look at his back pedigree. So, let us compare why that tiny bit more in percent may actually be a huge bit more in actual genes:
Antshar
through sire Sere to English sires Yunak, Koshut and Forthingbrass ( 2x )
dam Agawa was pure
Tshakan
through sire Sere to English sires Yunak, Koshut and Forthingbrass ( 2x )
dam Guldshakhan was pure
Serasker
through sire Sere to English sires Yunak, Koshut and Forthingbrass ( 2x )
through dam Sayat to English sires Burlak and Forthingbrass ( 3x )
It is the impure female line which adds another 3 traces back to Forthingbrass, as a whole Serasker's pedigree features him 5 times, running down both the male as well as the female lines, with 8 English bloodlines all put together.
What is the saying? If it looks like a duck, quacks like a duck, moves like a duck, it likely is a duck... and in the case of Serasker it is quite clear, that his relatively low infusion percentage does not even come close to realistically quantifying the heavy import made on his genes. It is indeed obvious that he carries quite a bit more English Thoroughbred genes than a mere calculatory 3%.
Such cases can be found everywhere within the breed today and as Serasker also demonstrates, they are currently preferred by selection and grading. Looks and gaits are not the only way the percentage of infusion can be qualified and properly quantified. Other means are e.g. character, health and speed on the racetrack. Any Teke considerably faster on the racetrack than his purer contemporaries has to be viewed with a close look at his back pedigree, just as Teke which show non-Turkoman character traits or lack Turkoman character values.
As with Serasker, the combination of sheer calculated infusion percentage plus a look at the back pedigree is a valuable means to judge how much of the English Thoroughbred we see in any given Akhal Teke. Add to that a close look at the properties shown in the first two generations and an evaluation is absolutely feasible. By the way this was and is being done for centuries by warmblood breeders and none of them would mock the method.