How influential is dam sire versus sire to horse ability?

Question

I'm looking at doing some analysis for horses in Smartform and want to know if it's worth looking at dam sire as well as sire.  Is there some accepted wisdom on how influential the horse's dam sire is compared to the horse's sire - eg. 70% 30%?   Is it worth looking at the dam sire form at all, in fact?

Answer 1

From the point of view of pure biology the ratio should be 2:1 in favour of the sire.

Mammals inherit genetic characteristics equally from both parents. Thus horse X will inherit 50% of his genetic characteristics from its sire, and 50% from its dam, while the dam will herself have inherited 50%  from her own sire (horse X's damsire). The overall influence on horse X's genetics is therefore 50% for the sire and (50% x 50%) = 25% for the damsire - a 2:1 ratio.

I did some analysis in this area a few years ago and found that:

a. the 2:1 ratio works about right in practice

b. sire and damsire records seem to be a markedly better predictor of distance preference than of racing ability

c. if you want to analyse ability, you need to take a horse's gender into account. As a group, fillies achieve lower overall ratings than colts and it's best either to analyse the two gender groups separately or to build in a sex adjustment.

Comments

Thanks - v. useful.  Interesting re. records predicting distance - did you look into going preferences too?

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Although it was some time ago when I did the analysis, I remember trying to look at going preferences but being hampered by lack of data.

Since 2003, about two thirds of turf flat races in Britain and Ireland have been on ground that was officially good or good-to-firm. Genuinely soft or heavy ground occurred in less than one-eighth of all races. This means that most of the actual race performance data is clustered in a narrow going band, and that there's only limited data on soft-ground performances - I was therefore only able to draw meaningful conclusions for the most prolific sires and damsires.

However, this discussion is rekindling my interest! I may dust off the data and see if a fresh approach works better ...

Answer 2

It is always worth looking at all angles because if you can find one where other people aren't looking then you have a good chance of finding a profitable angle. It sounds like you may be interesting in reading more about the Dosage Method. You can find this in the back of Nick Mordin's book Mordin On Time, from a blog post I wrote about it at http://www.raceadvisor.co.uk/the-dosage-method-–-the-alternative-analysis-tool/ or on the official website of http://www.chef-de-race.com/