HorseBytes
Pedigree analysis for bloodstock buyers

Every lot in the catalogue, read for speed and stamina.

Tell us which sale you're going to and what you're looking for. We analyse every pedigree and every family page in the catalogue, and send you a ranked shortlist of sprinters, milers, middle-distance horses and stayers — before you set foot on the sales ground.

Book a sale report See a sample report →
October Yearling Sale, Book 1 — report
Sprinters Milers Middle distance Stayers All lots
LotPedigreeClassFamilyTrip
250Mehmas × Soft PowerGr.1 dam6.1fSprinter
361Blue Point × Anna LawGr.1 dam5.8fSprinter
277Frankel × Swirral EdgeGr.1 dam6.3fSprinter
Best relatives, Lot 361: Battaash (dam's produce) — Nunthorpe Stakes, Gr.1
470 lots analysed in a single yearling sale
602 catalogue pages read — every family, every lot
419 lots judged on real family race records
2,500+ black-type races weighed for distance

A 600-page catalogue. A week to read it properly.

Every buyer wants the same thing from a catalogue: which lots are bred to do what they want, and which families actually deliver. Finding out means reading hundreds of dam pages, cross-checking pedigrees and remembering which races are run over which trip. We do that reading for you.

Too much to read

A single book can run to hundreds of lots, each with three generations of family history in small print.

Distance is guesswork

Catalogues name the races a family won, but not how far they were. Sprint family or stayer? You have to know every race by heart.

Dosage alone misleads

Classic dosage ignores today's stallions and every mare. On its own it can call a middle-distance family a sprinter.

How it works

Tell us the sale. We do the rest.

1

Tell us your brief

Which sale you're going to, colts or fillies, the trip you want, and any lots already on your list. That's all we need.

2

We analyse every lot

Every pedigree and every family page in the catalogue — cross-checked, with the right horse found even when dozens share a name.

3

You get your shortlist

A report ranking every lot by trip and family class, the lots that fit your brief picked out, and the evidence behind every verdict. We're happy to talk it through.

Two lenses on every lot

What the pedigree suggests — and what the family proved.

Family evidence takes every black-type race won by the dam, her foals and the second and third dams' families, looks up its distance, and weighs closer relatives more heavily.

Dosage scores the influential stallions in four generations of the pedigree — the classic Roman–Miller method, calculated exactly as the leading pedigree databases publish it.

In a recent 470-lot yearling sale the two agreed on fewer than half the lots. Our reports show you both, and flag where they differ.

Lot 69 · filly No Nay Never × Lady Babooshka
Dosage says Sprinter Speed stallions in the sire's line
Family says Middle distance Average winning trip 9.5 furlongs
Dam5 winners from 6 runners
Half-brotherRussian Camelot — Gr.1 Underwood Stakes, Gr.1 South Australian Derby
3rd damBella Colora — Gr.2 Prix de l'Opéra, 3rd in the 1000 Guineas
ClassGr.1-producing dam
What you get

A full report on the sale — and a shortlist for your brief.

Trip-guide shortlists

Sprinters, Milers, Middle Distance and Stayers — each ranked with the strongest families at the top.

Class at a glance

"Gr.1 dam", "Listed family (2nd dam)" — plus the dam's winners-to-runners record and her best relatives.

Family numbers

The female-line family number for every lot, and a Families tab showing which families are strongest in the sale.

Full dosage figures

Dosage Profile, Index and Centre of Distribution — plus separate speed and stamina shares that flag mixed pedigrees.

Every assumption on show

Every race and its distance listed on one sheet, so you can see — and question — how each verdict was reached.

The evidence, not just the answer

Every race behind every verdict is listed, so you can see exactly why a lot is called a sprinter.

Dosage explained

A century-old idea: read a racehorse's type from the stallions behind it.

Dosage estimates whether a pedigree leans towards speed or stamina by scoring the most influential stallions in the first four generations.

Early 1900s Colonel Vuillier A French cavalry officer notices the same great stallions recurring in champions' pedigrees, and devises the first "dosage".
1960s–70s Franco Varola Names the chefs-de-race — influential sires — and sorts them by the type of horse they pass on, from pure speed to pure stamina.
1981 Dr Steven Roman Turns the idea into numbers: the Dosage Profile, Dosage Index and Centre of Distribution used today.
2026 Still evolving The chef-de-race list continues to be updated, with 23 new chefs added in April 2026.

Five aptitude groups

BBrilliantSprinting, 5–6f
IIntermediateMilers, 7–9f
CClassicDerby trip, 10–12f
SSolid13–15f
PProfessionalTwo miles and beyond

Nearer stallions count more

Sire · 16 8 8 4444 2222 2222

Only stallions on the chef-de-race list score. Their points go to their group, and add up to the Dosage Profile — for example, Frankel's is 5-2-23-15-1.

Dosage Index (DI)

(B + I + ½C) ÷ (½C + S + P)

Speed points against stamina points. Around 1 is balanced; higher leans to speed.

Centre of Distribution (CD)

(2B + I − S − 2P) ÷ total

A balance point from +2 (all speed) to −2 (all stamina).

Useful — but flawed

Dosage has real blind spots, and taken alone it can badly misread a pedigree. Here's what goes wrong, and what we do about it.

See the six problems →
What's wrong with dosage — and how we fixed it

Six blind spots. Six fixes.

We tested classic dosage on a full 470-lot yearling sale. It called a Gr.1 middle-distance family a sprinter, rated sprinter-stayer crosses as "balanced", and put most European pedigrees in the stayers' column. So we rebuilt around it.

The problem with dosage What we do
1
The dam counts for nothingOnly stallions score. The mare — and everything her family has actually won — is ignored.
The dam's family is the centre of the reportThree generations of female-line race records, read straight from the catalogue: her produce, her class, her family number.
2
Today's sires score nothingFew current stallions are chefs-de-race, so the most important name in the pedigree — worth 16 of the 64 points — usually adds zero.
Real results decide, not theoryEvery lot's trip guide comes from the distances its family actually won over. Dosage is shown alongside, and falls back only when there's no family evidence.
3
The CD averages away the truthA sprinter crossed with a stayer and a pure middle-distance pedigree can both score a CD of exactly zero.
Speed and stamina shown separatelySeparate speed and stamina shares, plus a "Mixed" flag. In a recent 470-lot sale we found 86 mixed pedigrees the CD had hidden.
4
Thin pedigrees swing wildlyA pedigree with only a few dosage points can hit an extreme on one stallion, and the Dosage Index can shoot to infinity.
Evidence-weighted scoresPedigrees with little evidence are pulled towards the sale average, so a thin pedigree can't top a shortlist on one stallion.
5
Built on American racingIts benchmarks come from US dirt racing. European pedigrees, full of stamina influences, get pushed into the stayers' column.
Lots ranked against their own saleDosage is compared within the sale you're buying at, and family trips are measured in real furlongs of real races.
6
A number with no reasonsA DI of 1.67 doesn't tell you why — or whether to believe it.
Every verdict shows its workingEvery race behind every lot is listed, race distances are yours to edit, and gaps are flagged instead of guessed.
Why the dam matters

Dosage ignores the mare. Breeders never have.

Genetically, a foal takes its main DNA half from the sire and half from the dam. But the dam passes on things the sire never does: all of the foal's mitochondria — the energy factories in every muscle cell — and, to a colt, his only X chromosome. She carries the foal, feeds it and raises it.

Most importantly for a buyer, her record is evidence. A stallion has hundreds of foals, so his average tells you little about this one mating. A mare has a handful — and every one of them has run for the same family you're about to buy into.

That's why our analysis is built around the female line: what the dam, her foals and her family actually won, how far, and at what level.

What each parent passes on

Main (nuclear) DNA — over 20,000 genes50 / 50
Mitochondrial DNA — 37 genesDam 100%
A colt's X chromosomeDam 100%
Sire Dam

Research into whether a mare's mitochondrial type affects racing ability is still mixed, so we don't score it. What we do score is her family's proven racing record.

Family numbers

Every thoroughbred goes back to a handful of founders.

Three stallions imported into England around 1700 — the Darley Arabian, the Byerley Turk and the Godolphin Arabian — founded the breed's male lines. On the female side, every thoroughbred traces its bottom line back to one of a few dozen foundation mares.

1890s

Bruce Lowe's numbers

The Australian researcher traced classic winners' dams back to 43 foundation mares and numbered the families by how many classic winners each had produced. Families 44–50 and separate American and colonial families were added later.

13-e

Families and branches

The number is the family; the letter is a branch within it. Lowe's claim that some families were "running families" and others "sire families" hasn't stood up — which is why we measure each family by what it has actually won.

DNA

What the science found

Mitochondrial DNA passes unchanged down the female line, so it can test the old records — and it found some horses don't match their recorded family. On the male side, the great majority of today's thoroughbreds trace back to the Darley Arabian.

Which families are strongest in this sale?

Every report includes a Families tab: each female family in the catalogue, how many lots it has, how many come from Gr.1-producing dams, and which trip it leans to — measured on real results, not a 130-year-old theory.

FamilyLotsGr.1 damsLeans to
[No.][n][n][Miler]
[No.][n][n][Middle distance]
[No.][n][n][Sprinter]
Built to be trusted

Our method checks its own work.

Pedigree data is full of traps — dozens of horses called Frankel, countries recorded differently, races that change their names. Our analysis is built to catch them rather than guess.

The right horse, every time. A sire or dam is only accepted when its own sire matches the catalogue pedigree.

Arithmetic double-checked. Every pedigree's dosage is recalculated and compared with the published figure.

Gaps shown, never hidden. Anything we can't find or confirm is flagged in your report, not quietly guessed.

Tested on a real sale. In a 470-lot yearling sale every sire, dam, grandsire and damsire we read matched the official sale list.

Services

For one sale, or the whole season.

Every brief is different, so we agree the scope and fee with you before we start. Get in touch and tell us about your sale.

Sale report

Every lot in the catalogue ranked by trip and family class, with the full evidence.

Shortlist to your brief

Tell us what you're looking for. We pick out the lots that fit, explain why, and talk you through them.

Talk to us

Season service

Reports and shortlists for every sale you attend, all season.

Questions

Do you predict how good a horse will be?

No. We tell you what the pedigree and family point towards — trip and class of family — so you can focus your inspections. Conformation, the horse in front of you and your own judgement still decide.

Which sales do you cover?

Our method has been built and tested on a major UK yearling sale. Tell us the sales you're going to and we'll confirm we can cover them.

When do I get my report?

Once the catalogue is published — in time for your inspections. Tell us your sale when you book.

What do you need from me?

Just the sale you're going to and what you're looking for. Your report comes as an Excel file you can sort and filter, with your shortlist on top.

Going to a sale? Let's look at the catalogue together.

Tell us which sale and what you're after, and we'll take it from there.

Send an enquiry → A short form — we'll reply personally.