Comments on: 100 years of Derby data: inbreeding sire line x broodmare sire line

By: LarryK

LarryK — Mon, 22 Mar 2010 11:57:40 +0000

Sid, Thanks for a great piece, loved it.

By: sidfernando

sidfernando — Thu, 18 Mar 2010 03:22:23 +0000

Well, i don’t know, Stanley, if you can expect a graded SW 25% of the time you inbreed. Some forms of inbreeding work better than others, for starters. Read Roger Lyons’ latest post for a look at combing Storm Bird (by Northern Dancer) with Nijinsky (by Northern Dancer), for example.
http://werk2.werkhorse.com/experts/index.php/2010/03/16/pedigree-pseudo-science/

By: stanley

stanley — Wed, 17 Mar 2010 16:46:19 +0000

sid,

interesting piece leaves me in a quandary about the subject i had with a knowledgeable friend. i read (and tested myself by random selection of such, weekly for a year) the theory that no more than 20-25% of graded stakes winners were a result of inbreeding within 4 generations. My study results were consistent with that. So i posed the question to my friend: why inbreed if 3 out of 4 occurences fail to produce a graded SW. His reply: Why not if you can expect a graded SW 25% of the time! What’s your take on this?

By: Calvin L. Carter

Calvin L. Carter — Wed, 10 Mar 2010 19:36:03 +0000

Sid,

Yes, I did notice that – I thought you would find it interesting. Again, thanks for the article.

By: sidfernando

sidfernando — Wed, 10 Mar 2010 18:14:15 +0000

Roger Lyons is going to get me a statistically meaningful sample tonight, extracting data from the 2009 September sale. However, my little “study” covering 100 years of Derby data was meant as nothing more than a cautionary tale; after all, there’s been only 1 Derby winner inbred as close as 3×3 sire line x broodmare sire line, so if you were looking at a Derby prospect in a yearling sale inbred, say, 3×2 to Mr. Prospector in this fashion, or perhaps planning a classic mating the same way, perhaps you’d need to think twice? Or at least do more research.

FYI: This post was actually inspired by a pedigree guru who is planning a “Derby horse” for a client that will be inbred 3×2 to Mr.P!

By: David Crone

David Crone — Wed, 10 Mar 2010 16:01:36 +0000

Interesting. Do you have any data on how many horses have attempted the feat? Or what percentage of the Thoroughbred population is inbred in this manner? If only 4% of Thoroughbreds are inbred sire line x broodmare sire line then this data doesn’t mean much. If 20% are then perhaps it becomes more meaningful. Then we also have to wrestle with the issue of sample size. These are all reasons why I have always disliked the traditional use of Derby history as a predictor of the future. These are all independent running with countless independent variables. They simply do not offer a proper forum for “scientific” study.

By: sidfernando

sidfernando — Wed, 10 Mar 2010 14:57:38 +0000

Calvin, thanks for that. It’s ironic that his comments in 1909 begin one year before my look at the Derby from 1910 to 2009.

By: Calvin L. Carter

Calvin L. Carter — Wed, 10 Mar 2010 00:53:11 +0000

Sid,

Thank you for the article on inbreeding. I found it interesting that Burchard Von Oettingen reached a similar conclusion in his book â€œHorse Breeding In Theory And Practice,â€ published 1909 by Sampson Low, Marston & Co.

â€œâ€¦There has been also much damaged by exaggerated inbreeding in the American Thoroughbred breeding. Among the many instances of 0 free generation I have not found a single one in the American Stud Book which has been of importance to breeding. I have only found one good racehorse in the American Breeding, and that is Henry 1819 by Sir Archy-Doimed (i.e. 0 Diomed), celebrated by his famous match with the American Eclipse in New York, 1823.â€ – page 233