Most inbred and outcrossed pedigrees

[hpkingjr]

I was thinking about how much inbreeding and how little outcrossing I see when I look at the coefficient of inbreeding at the bottom of the linebreeding page. Question:

What is the most inbreeding in a pedigree you've seen and what is the most outcrossed pedigree?

An example of an outcrossed pedigree:

http://www.pedigreequery.com/index.php?search_bar=hypomating&query_type=hypomating&h=&hypo_sire=wilko&hypo_dam=relaxer&g=5&all=No&cellspacing=0&cellpadding=0&border=0&f=1&p=0&c=0&text_color=000000

8 Generation Coefficient of Inbreeding: 0.346%
Number of unique ancestors in 9 generations (711/1023) = 69.50%
Number of unique ancestors in generation 9 (346/512) = 67.578125
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Give the Pope and the King of England a horse and in thirty days, they'll be stealing halters.

[xfactor fan]

High Time

By Ultimus out of a daughter of Domino.

http://www.pedigreequery.com/ms+triple+sec

[brogers]

Winloc's Millie

http://www.pedigreequery.com/winlocs+millie
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Byron Rogers
Performance Genetics
www.performancegenetics.com

[brogers]

Interesting question though....

Geneticists believe that in any population there is an optimum level of inbreeding for the general fitness of the breed. It would be interesting to see if there was an optimal range of inbreeding for the thoroughbred to be bred towards. Are we already too inbred, or not inbred enough???
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Byron Rogers
Performance Genetics
www.performancegenetics.com

[hpkingjr]

[brogers]

If you were looking at an individual stallion, you would probably be better off looking at mean kinship and relationship coefficients. To do this you would need to separate all the horses by Awesome Again into two groups

Graded Stakes winners - there are 25 of these

Horses that raced at least 3 times and failed to win (placed or unplaced). You could even subqualify this group to be horses who didn't get a 60 Beyer or better. You probably only need 50 horses in this group.

You could then take an individual horse by Awesome Again, let's say an unraced yearling, and generate a Mean Kinship value and a Relationship Coefficient value for this yearlings pedigree.

A mean kinship value can be calculated for each horse against each population (GSW/Slow Horses) using a formula. Mean kinship gives a numerical value to how closely related the individual horse (the yearling in our case) is to each population. This gives us an important measure of just how rare an individual horses' unique combination of ancestors is in the entire population. Horses with a lower mean kinship values have relatively fewer ancestors in common with the rest of the population so you would be effectively able to see if a horse was more closely related to the group of graded stakes winners as a whole, or more closely related to the group of non winners as a whole.

The second step would be to create a relationship coefficient for the subject. This is a measure of pedigree relationship or the probable proportion of one individual's ancestors, that are identical to ancestors of a second individual so it is a one to one comparison. The coefficient of relationship provides a way of objectively assessing the similarity of two pedigrees by giving a number that is a direct measure of shared ancestry. In most populations, two individuals picked at random would likely have a RC of 0, a brother and sister 50% and identical twins 100%. Other relationships would fall between 0 and 50%.

In the case of our unnamed yearling he/she would have an RC of at least 25% (as Awesome Again is a constant), but they would also be compared individually against the other 75 horses (25 GSW/ 50 non winners) and RC values would be generated for each of these horses so that you would have a good idea who the pedigree as a whole was closely related to.

Of course, the presumption then is that if a yearling is more closely related to the graded stakes winning population as a whole, and more closely related to stakes winners individually than other horses, that they are more likely to become stakes winners (i.e it is predictive). This is a decent presumption to make and one would have to do significant research to work out if this was true or not.
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Byron Rogers
Performance Genetics
www.performancegenetics.com

[hpkingjr]

I really enjoyed the thought process and steps involved in trying to quantify the probability of quality and success in a pedigree. Are there any examples that you are aware of that have been done with any stallion or group of stallions?
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Give the Pope and the King of England a horse and in thirty days, they'll be stealing halters.

[brogers]

None that I am aware of.

I know that there are people that have done a fair amount of work on inbreeding coefficients in a manner similar to yours (i.e get a list of horses by a stallion and look at their inbreeding coefficients and see if the SW are more or less inbred than the population at large), but I haven't seen any that have compared one-to-one 'likebredness' (a relationship coefficient), nor a mean kinship (compare one horse against a population of the sire).

The Jockey Club are looking into programming inbreeding coefficients into their Pedigree Analysis system. Once they have the inbreeding coefficients properly programmed within that system, doing comparatives like this wouldn't be hard. It would be of interest to know if you had a yearling by a proven sire if he was more or less 'likebred' to the best stakes winners by the sire. Of course you would need to prove that being more closely 'likebred' meant that you were more likely to become a stakes winner, which may or may not be true.

The advantage the Jockey Club probably has is that they would have more completeness of pedigree (COP) than other databases so their inbreeding coefficients would be the most accurate. Creating an inbreeding coefficient when you have ancestors missing underestimates the inbreeding coefficient.
_________________
Byron Rogers
Performance Genetics
www.performancegenetics.com

[deaky]

[vineyridge]

One of the best Advanced event horses of a couple of years ago was an oops pasture breeding. Pure TB, but his uncle was his father. He was never really a 4* horse, but he was darned good at 3* and dressage. Apparently there is a huge difference between kin relationships and the kind of inbreeding that uses the coefficient of inbreeding as a guide.

The King Ranch study found individuals with as much as 25% of a single horse in an 8 generation pedigree but a perfectly acceptable (low) coefficient of inbreeding. Of course the herd was developed initially with very intensive inbreeding on three sires--Old Sorrel, his sire Hickory Bill, and his grandsire Peter McCue. This was grandfather/granddaughter or uncle/niece inbreeding. But they knew what traits they were trying to fix, and kept all their produce that didn't exhibit the desired traits out of their breeding pool.

The King Ranch study is a scientific pedigree analysis back to 1915 of the current breeding population of Quarter Horses at the King Ranch. It was published in 2010 and was done by Texas A&M at Kingsville. It mostly focuses on the use of sires.
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Thread Killer Extraordinaire

[hpkingjr]

[vineyridge]

Thoroughbreds having been a closed book for more than 200 years and also having suffered breeding fads means that you are going to have lots of ancestor loss. There is a body which has published "The Conservation Breeding Handbook" on rare breed preservation and it is, I am told, the best discussion out there on how to maintain genetic diversity in limited populations--although with the million or so TBs out there, the population isn't really limited.
http://www.albc-usa.org/store/store-conservation.php

Here's a link to the scientific study on King Ranch horse genetics:
http://pas.fass.org/content/26/1/1.full.pdf+html
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