Inbreeding, Linebreeding, Outcrossing

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   I think these three words describe the same thing - duplications in pedigrees - duplications that are in both the sire and the dam of the horse.Almost all discussion about duplications stops at the sixth generation (2+4+8+16+32+64 = 126 ancestors).  Often discussion ends at the fifth generation.

Why?
Because it is too difficult to write out 7 or 8 or 9 or 10 or more generations on paper or display them on a computer screen.

I am getting a bit obscure here but when you add an extra generation e.g. go from a 5 gen pedigree to a 6 gen pedigree the duplication groups can change, and the same going to a 7 gen pedigree from a 6 gen pedigree, and so on.
The correct way (my opinion) to identify duplications if to take the ancestor with year of birth closest to the subject horse and look for any duplication of that horse.  Then move to the next closest ancestor by year of birth and repeat.
Of course analysing pedigrees by identifying duplications is nothing more than a short-hand way of reducing a pedigree to a handful of ancestors.

A while back I wrote a program to identify the duplications in 10 gen pedigrees (2+4+8+16+32+64+128+256+512+1024 = 2046 ancestors).

Often people treat duplications (or inbreeding) as an indivisible unit.
The duplicated ancestor group can be males (sires) or females (dams), and there are three possibilities for each group.
A simple example is a duplication group of a sire twice in a pedigree.  He is a male.  The offspring of that male twice can be two sons, two daughters, or a son and a daughter.

I will post below the 10 generation duplication groups of 15 horses: 9 high rated; 6 low rated.
When I did the work the idea was to see if there were differences between the duplication groups of the high rated and the low rated horses.
If there is a difference it is that the low rated horses have more groups of duplicated sires producing sons only (highlighted in grey) close up in their pedigrees i.e. in the first 10 groups, often in the first five groups.

It would be great if a 10 generation prdigree could be reduced to one number to identify quality.