OTO is home to 18 studbooks and 3 associations that horses can be registered under! Both studbooks and associations fall under the broader category of "registries".

A studbook is a place where Warmblood horses can be registered. Each association inspects stallions and mares to enter their studbook: a list of approved stallions or mares that meet the ideals for that association. Any horse of Warmblood breeding that is by an approved stallion and out of an approved mare is eligible to be registered with the corresponding studbook.

An association is also a place that horses can be registered under, however they are restricted in what breeds they will register. For example, the Sport Thoroughbred Association will only register horses of pure Thoroughbred breeding. On OTO, the registries also approve horses to a "studbook", in order to create a list of top quality mares and stallions within the association. The three associations on OTO are Stock Horse, Thoroughbred and Trakehner.

Registry Basics

Registries (with the exception of closed associations) are "open", meaning that any Warmblood can be registered in any registry.

In order to get your horse registered, you must take them to an Inspection. As a result of getting your horse inspected, you will get a judge's card that evaluates them on the 6 Conformation areas, and will give you a clue as to whether the horse is best suited to Dressage, Jumping or may be a candidate for Eventing.

All foals initially presenting for inspection will join the General Book for that registry. If you have a good mare or stallion, you may re-present them to upgrade them to Breeding Status once they are older. Once they have achieved breeding status, they will be moved to another book.


Studbooks are where all horses eligible to breed within a registry are listed. Mares have 5 studbooks they can be sorted into, whereas stallions are only listed in the Stallion Book. Horses that have not been presented for riding tests are found in the General book.

When a horse enters a studbook, the studbook division will be noted on their page, preceeding the studbook prefix in brackets [ ] before their ID number. For example, horse #G-[AWR]-1 is a General book American Warmblood.

Each studbook has seven divisions for horse registration. They are as follows:

G - General Studbook
This is for general registration. Horses with approved parents can be registered under this division of the studbook.

S - Stallion Book
This is where approved, entered stallions are listed. Stallions must be riding tested and inspected to enter the Stallion Book.

MM - Main Mare Book
Main Mare Book mares are the cream of the crop! Only top quality mares are listed in this book. To qualify for the MMBook, candidates must be:

M - Mare Book
Mare Book mares are excellent quality mares. To qualify for the MBook, candidates must be:

P1 - Pre-Mare Book I
Pre-Mare Book I mares are good quality mares of Warmblood breeding. To qualify for the P1Book, candidates must be:

P2 - Pre-Mare Book II
Pre-Mare Book II mares are good quality mares to be incorporated into Warmblood breeding. To qualify for the P2Book, candidates must be:

A - Auxiliary
The Auxiliary Book mares are mares that do not meet the other book qualifications. The primary purpose of the Auxiliary Book is to introduce Stock Horse lines into Warmblood pedigrees.


Each registry and studbook has its own brand. Mares in books P1 or higher or stallions in the Stallion Book are eligible for branding.


The registries currently only have two fees, for inspection and riding tests.

Highest Ranked Stallion and Mare

On each registry's page, you can find a list of their 5 highest ranked stallions and mares. This ranking is based on progeny's earned points! A stallion or mare that produces top quality dressage, jumping and eventing horses will generally have the most points, and thus earn the title of highest ranked stallion or mare.

Studbooks and Registries

Shows and Inspections