I always wondered how can you identify horses. It maskes interesting reading :-

Being able to formally identify a horse is important for many reasons.  Definitive identification is vital for entry into a breed or sports register, for competition and racing records as well as to prove ownership of the horse in question.  Many horses now have a passport, into which a physical description including height, sex, colour and any other identifying markings are recorded.

Height
Traditionally the standard measurement of height in the horse is the ‘hand’, which is equivalent to four inches (10cms). Measurement is taken from the ground to the highest point of the withers.

To obtain an accurate measurement it is important to ensure that:

The area on which the horse is standing is smooth and level
The horse is standing squarely on all four feet with the fore feet together
The head is lowered bringing the poll in line with the withers
If the horse is shod, a half-inch (approx 1.25cm) is deducted from the measured height to allow for depth of the shoes
Sex
Sex is another important descriptor to use when identifying a horse.  Common nomenclature is listed below.

Mares are females over 3 years of age.
Stallions are un-castrated males over 3 years of age.
Geldings are castrated males of any age.
Foals are horses from birth to end of first year.
Yearlings are horses in the first year after birth.
Two-year olds are in the second year after birth.
Colts are young males up to three years of age.
A filly is a young female up to three years of age

Colour
It is important to remember that coat colour can change throughout the course of a horse’s life e.g. some may be born black and within a few years will have turned grey.

Leg Markings
A description of white markings on the leg should accurately as possible describe to what height they extend e.g. white pastern and fetlock, white to half cannon or white to two-thirds cannon.
Small black spots on the coronary band of a white lower limb are described as ‘black marks on the coronary band’.
Whorls
A whorl is a patch of hair that grows in the opposite direction to the rest of the horse’s coat. They are commonly found in the stomach area, on the face and neck and sometimes on the stifle and hock areas.  Whorls are permanent and do not change throughout the horse’s life; they are therefor used as an additional permanent identifier.

Additional Identification Methods

Microchips
A microchip can be inserted into the horse’s nuchal ligament in the neck via a hypodermic syringe. The chip has a unique identifying number which is assigned to that specific horse. The chip emits an invisible radio signal, which can be detected by a microchip reader.  This type of identification is said to be permanent and only has to be done once in the horse’s life. In the UK, any horse or pony born after the 1st of July 2009 must be micro-chipped by law.
Hot Iron Branding
This traditional method of permanent identification uses a branding iron that is heated to a high temperature and applied to the horse’s body.  The heat kills the hair and skin in that area resulting in a permanent identifying mark. The brand may consist of symbols and/or numbers to identify the breed of horse, the specific stud or station that the horse has come from and the horse’s year of birth. The brand may be applied to the shoulder, quarters or the neck. Hot iron branding is considered inhumane in some countries and other methods of permanent identification are used instead.

Hoof branding is another form of hot iron branding where the hot brand is applied to the horses hoof.  As the horses hooves grow continuously, this procedure has to be carried out every 6 months or so and is therefore not permanent. Hoof branding is considered to be more of a theft deterrent, rather than a permanent form of identification.

Freeze Branding
Freeze branding uses a branding iron that has been frozen (-196oC) using liquid nitrogen.  The hair is clipped away from the brand site and the iron is applied.  An alternative to liquid nitrogen is using a mix of dry ice and methylated spirits (-78oC). The mixture quantities should be 1kg of dry ice and 1 litre of methylated spirits for 1-3 horses.

Depending on country, state or region, there are different acceptable places for freeze branding. For example, In the UK it is usual on the horse’s neck or in the saddle region just behind the withers, whereas in Queensland, branding is only permitted on the shoulder, thigh or quarter. The brand alters the pigment producing cells in the hair and skin and after healing, the brand appears as a clear, permanent white mark.

Lip Tatoo
Lip tattoos are commonly used in America to identify race horses.  A permanent tattoo is applied to the inside of the top lip, which is linked to the horse’s breeding, ownership and competition records. The tatoo contains a mixture of numbers and letters, which identify the horses breed and date of birth.  Lip tattoos are permanent and only need to be applied once in the horse’s life.