Sire, dam and damsire explained: reading a racehorse pedigree

The three names on every pedigree line

Every thoroughbred’s breeding is summed up in three names: its sire, its dam and its damsire.

In racing shorthand a horse is written as by its sire out of its dam, with the damsire in brackets: a colt by Dubawi out of Example (Galileo) is sired by Dubawi, his mother is Example, and Example’s own sire was Galileo. A racecard that is short of space often gives only the sire and damsire, as “Dubawi – Galileo”, because the dam’s name tells you less on its own unless you know her other foals.

Why the damsire gets its own name

The damsire is the one grandparent named on a racecard because he is the quickest summary of the dam’s side. Most mares have only a handful of foals, so the dam’s own record as a breeder rarely gives a usable sample. Her sire, by contrast, will have daughters producing runners all over Britain and Ireland, so his influence through those daughters can be measured across thousands of runs.

Some stallions are better known as damsires than as sires: their daughters keep producing good runners long after their own racing progeny have retired. That is why the damsire figures on this site are a separate record from the same horse’s figures as a sire.

Brothers, sisters and half-siblings

Racing uses sibling terms in a particular way. A full brother or full sister shares both the sire and the dam. A half-brother or half-sister, in racing, shares the dam but has a different sire. Horses that share only a sire are not usually called half-siblings, because a popular stallion can have hundreds of foals a year and the link says very little.

When a racecard comment says a horse is “a half-brother to a Group winner”, it is telling you about the dam: she has already produced a good horse by a different stallion.

What breeding tells you, and what it does not

Pedigree is most useful where a horse has little or no form to go on:

• Debutants and lightly raced horses. A two-year-old on its first run has no form at all, so the sire’s record with first-time-out runners is one of the few things you can check.
• New ground. A horse trying soft ground for the first time may be bred for it, or bred for fast ground. The going guide covers how going preference passes down.
• A step up in trip. Stamina is partly inherited, so the sire’s distance record, and the damsire’s, are a clue to whether a horse will stay a longer trip.

What breeding cannot do is override a horse’s own record. A sire’s figures are averages across many horses, and any single foal can take after the other side of its pedigree, or neither. Once a horse has run several times on a type of ground or at a trip, its own form is better evidence than its father’s.

Reading a sire’s statistics

Sire figures look precise, but they need the same care as any other statistic.

• Win rate needs its sample. 20% from 50 runs and 20% from 5,000 runs are very different things. Always read the number of runs next to the percentage.
• A preference can be a small difference. A sire whose runners win 19.6% on firm ground and 19.4% on good has a firm-ground figure that is technically highest, but the two are effectively the same. Look at the whole table, not just the headline band.
• Impact Value (IV) compares with everyone else. IV is a group’s win rate divided by the win rate of all runners in the same races or at the same course. 1.00 means exactly average; 1.30 means 30% more winners than average. It corrects for the fact that some courses and race types have bigger fields and lower win rates for everybody.
• Good stallions get good mares. The best sires are sent the best-bred mares, so part of their record reflects the mares, not just the stallion. That is one more reason to read a sire’s figures as background rather than proof.

Pedigree on TRF

Open any runner on the racecards and its breeding section names the sire, dam and damsire, each linking to its page where we have one.

The sire pages show each stallion’s progeny across UK and Irish racing: overall win rate, the record on each going and at each trip with the runs behind every figure, and first-time-out and two-year-old win rates. A going or trip preference is shown only when that band has enough runs behind it to mean something; otherwise no preference is shown.

The damsire pages do the same for runners whose dam is by that stallion, so they measure his influence through his daughters, kept separate from his record as a sire, with course figures and their Impact Value. The Breeding Lab brings today’s runners’ pedigrees together, with sire and damsire combinations and a mare’s other foals.

Sire, dam and damsire: frequently asked questions

What is a damsire in horse racing?

The damsire is the sire of a horse’s dam: its maternal grandfather. He is also called the broodmare sire, and racecards often show him in brackets after the dam’s name.

What is the difference between a sire and a dam?

The sire is the father and the dam is the mother. A horse is described as “by” its sire and “out of” its dam.

What does “by” and “out of” mean on a racecard?

“By” names the sire and “out of” names the dam. “By Dubawi out of Example (Galileo)” means the sire is Dubawi, the dam is Example, and Example’s sire was Galileo.

What is a half-brother in horse racing?

A horse with the same dam but a different sire. Horses with the same sire only are not normally called half-brothers.

Does breeding matter more than form?

No. Breeding is most useful when a horse has little form on today’s ground or at today’s trip. Once a horse has a record of its own in those conditions, that record is the better guide.

What is a sire’s Impact Value?

The win rate of the sire’s runners divided by the win rate of all runners in comparable races. Above 1.00 means more winners than average, below 1.00 fewer. Always read it with the number of runs behind it.