Measuring Ancestor Appeal
by Roger Lyons
Recent posts about Dixieland Band and Graustark preceded their broader context, which arrives as a table, titled “Ancestor Preferences of Major US Sires.” The table covers 164 ancestors and reflects, among other things, how well or poorly individual ancestors of broodmares are playing to the contemporary stallion population. Links to three different versions of the table are provided below.
The table is very simple once you catch on to the concept. To over-simplify, there’s about a 31% chance that a stallion whose name you pick out of a hat is going to react well with Storm Cat in the ancestry of a mare and only about a 9% chance of an unfavorable reaction. That leaves about 60% that do okay with Storm Cat, but not many breeders dream of results that are okay.
If your mare is by Storm Cat, the odds are not bad that you’ll draw a suitable stallion by chance, at least in that respect. However, if her dam happens to be by Halo, with which only 13% of the stallion population react favorably against the 22% that react unfavorably, it’s more complicated. Thus do questions of compatibility arise from the layers of a mare’s ancestry.
Clearly, the breeding of some mares renders them far more flexible as to the selection of a mate than other mares. Ideally, you would want a stallion to have high stike rates with a mare’s entire ancestry. Some mares may have a range of such options, but for other mares there’s no such stallion.
Anyway, for each ancestor, I surveyed 71 proven sires to determine, first, how many of them sired foals out of at least 10 mares in some descent of the subject ancestor. Second, the qualifying sires were divided into two groups: 1) those that, from mares in some descent of the subject ancestor, had strike rates significantly above their overall records and 2) those that had significantly lower strike rates with those mares.
Here’s the legend for the resulting table:
Ancestor–the subject ancestor as represented by broodmares.
Sires–the number of stallions (from among the 71) that sired 10 or more foals with mares representing the ancestor.
Approve–the number from the “Sires” group with significantly higher-than-average strike rates.
Approve%–the percentage of “Sires” with significantly higher-than-average strike rates.
Disapprove–the number from the “Sires” group with significantly lower-than-average strike rates.
Disapprove%–the percentage of “Sires” with significantly lower-than-average strike rates.
There are three versions of the table, one listing 164 ancestors by “Approve%” rank to show them in order of the frequency of high strike rates by the stallion sample; another listing them by “Disapprove%” rank to reflect the downside risk; and then an alphabetical listing so you can have fun looking them up individually.
Bear in mind, the survey includes only US sires. Danzig’s approval rating of only 14% and disapproval rating of 23% would be vastly different based on a survey of European or Australasian sires. Nevertheless, Danzig is a problem for a lot of US stallions.
I’ll comment further on this table in future posts, beginning with the reason why Native Dancer’s approval rating is the lowest in the list.
Of ocurse the real trick is knowing exactly which particular matches fit which categories. Well, actually, there are more tricks than just that, eh?
February 20th, 2011 at 8:22 amBasically, to determine which category a stallion should go in, his strike rate with mares in descent of the given ancestor is compared with his overall strike rate. If the actual strike rate with those mares is significantly higher than with all mares, he goes in the approve category, if significantly lower the Disapprove category. In most cases, the “not significantly different” category contains the majority of stallions.
February 20th, 2011 at 9:51 amCornish Prince seems to have really suprising numbers. Wonder why you don’t see him more often in pedigrees. Same for Irish Castle. Dixieland Band, too, is a bit of surprise. I guess it isn’t necessarily how big the percentages are but how potent the good ones are, how poisonous the bad.
February 21st, 2011 at 6:32 pmAnother one that’s even more of a mystery to me is Amerigo (1955). He’s been near the top of the list for years. Besides surprises, how about this coincidence? Secretariat and Sir Gaylord are listed consecutively in the table by Approve% by virtue of having the same Approve%.
February 22nd, 2011 at 7:57 amAnd, Greg, check the comments section of “Graustark’s Hard Edge” for Frank Mitchell’s response to your question about differences between His Majesty and Graustark.
February 22nd, 2011 at 8:01 amSo, one might guess that it’s Somethingroyal influencing things here?
Thanks for pointing me back to the Graustark posting.
February 22nd, 2011 at 10:21 am