Chapter 3



Identification procedures

One of the most essential aspects of stud farm management is the effective identification of mares, particularly those visiting animals that are not well known to the stud staff. Unfortunately, this is an area that is sometimes neglected and can then cause considerable problems.

There are a number of effective means of identification, each with some advantages and some disadvantages. Failure to identify a mare correctly at a stud can have catastrophic financial implications. Stallions are usually relatively simple to identify because they are generally managed in an individual fashion, whereas the mare population on a stud may vary markedly.

The methods available for identification of the animals include several visible means, some hidden means and some that rely on documentation. Most of the effective methods are permanent, but temporary identification can be useful under some conditions (e.g. short-term movement to a stud farm).

Hoof branding

Hoof branding (Fig. 3.1) is a semi-permanent method of identification, but of course the marks are lost as the hoof grows out. Also, it is possible to tamper with the marks by altering the figures to some extent. Nevertheless, it is a reasonably effective way that is painless (hopefully) and will certainly be identifiable for some 4–6 months. It can be repeated as many times as necessary.

Usually a postcode/zipcode or telephone number is used, which can be spread over all four hooves.

Tattoo (lip/gum or ear)

A tattoo is a recognized way of identifying horses that relies upon the ancient art of permanent skin coloring. Usually the tattoo is applied to the soft pink lining of the inside of the lip. This enables the dark-colored pigment to be easily recognized. The shape of the lip, however, makes it difficult to apply the tattoo with a consistent degree of accuracy and so experience is required.

Freeze marking

Freeze marking (Fig. 3.2) has been used for many years as a means of identification. It relies upon the change in color of the hair from body color to white when the skin is subjected to a defined cycle of freezing. The freezing is not enough, however, to cause serious freezing leading to ulceration of the skin. In gray horses the method requires a harder freeze because the intention is to create a hairless mark rather than just a change in the color of the hair coat. A white mark on a white-haired horse would probably not be obvious! In many cases the freeze mark is not very obvious until the area is clipped, but most freeze marks are obvious from a distance.

Hot branding

Hot branding (Fig. 3.3) commonly takes two forms. The first is a standard identification mark that is used for specific breeds of horse. The second is some form of specific identification; historically, this was used to identify the owner of the horse or its origin, but it could equally be used to add numbers and letters in combination so that the animal can be identified permanently. The brand is usually applied at an early age (when restraint is more practicable). The effect is obtained by creating an obvious, defined shaped scar. No hair grows on the scar and it is therefore visible from a distance and regardless of the hair coat status (winter/summer).

Microchip identification

Microchip identification of horses is gaining much credibility as more and more chips become available and more and more microchip readers are held by police, slaughter houses, customs, and welfare and charitable institutions. Although there are the usual horror stories of nasty injection reactions and migrating chips, these are extremely rare; indeed, they may be less common than physical injury to the exact site of the chip placement.

Identification by natural markings/scars (permanent alterations)

This has been used for many years as a means of categorical identification. It relies upon the accurate and detailed sketching and written description of all naturally occurring white marks and hair whorls. Often it includes certain permanent acquired markings.

Photographic identification

Photographic identification has not gained the reputation or universal application it perhaps deserves. There is scope for the inclusion of color pictures in a sealed tamper-proof plastic sheath. However, photographic quality varies and in some cases it may not be helpful at all. For example, almost all Fell ponies are a very similar uniform color and so a photograph might not be helpful. Similarly, gray horses and Appaloosa horses will often not retain either the same color or the same pattern distribution. Some foals are born bay or chestnut and change to gray.

Blood typing (gene/DNA mapping)

Blood typing is helpful in establishing parentage but on its own does not help to identify an individual horse.

Tissue typing can, in theory, be performed from any body tissue, including clippings, hair, blood, semen or even cells taken from the cheek lining. In practice, it is usual to use hair or blood. The tissues can be stored indefinitely and the technology is becoming more readily available and cheaper with advancing scientific methods.

The genetic make-up of the tissue cells of an individual is totally unique. However, gene mapping is really an advanced form of tissue typing and provides no more information than the tissue type with respect to identification.


Routine vaccination is usually performed for a variety of diseases according to local disease-control requirements. For an effective immunologic response the animal needs to be healthy and have an active immune system. Stress, debility, illness or malnutrition can influence the response to a vaccine. All vaccines have a defined protocol that enhances the protective response in the vaccinated animal, but although most are regarded as beneficial some do have potential harmful effects and some are much less efficacious than others. Thus, the vaccine for tetanus is regarded as excellent protection whereas that for influenza can be less predictable. The nature of the disease and the organism itself has an influence on the efficacy of a vaccine.


In general, all horses are vaccinated routinely against tetanus using a standard routine. This involves a primary course of two intramuscular injections of tetanus toxoid followed by a booster vaccination after one year and then every alternate year.

Foals are usually considered to be effectively covered for up to 6–8 weeks of age through colostral transfer of antibody (see p. 374) provided that the mare received a booster vaccination in the last trimester of pregnancy. If a mare has not been vaccinated for between 1 and 2 years before foaling the duration of transferred immunity is probably inadequate.

If there is any doubt about either the effectiveness of the vaccination of the mare or the efficiency of colostral (passive) transfer of immunity (see p. 377) it is common practice to administer a single or repeated doses of between 1500 and 6000 IU of tetanus antiserum. This will usually confer effective protection for up to 12 weeks of age.3

The administration of a tetanus toxoid at, or shortly after, birth is controversial, but in theory at least there should be no particular problem with vaccination at 2–4 weeks of age.4 However, most authorities do not recommend vaccination at birth of a foal that has effective passive transfer on the basis that passive antibodies will interfere with active immunity for a primary vaccination. Repeated vaccination during this time may indeed result in poor long-term immunologic response to the vaccine, and in some cases there may be no effective response. However, some authorities consider that active vaccination in the face of passive maternal immunity is effective.5


Vaccination against influenza viruses (equine influenza A, types 1 and 2) is common practice in most areas of the world. However, there are a few places where the disease does not appear to exist and vaccination is not practiced (e.g. Australia and New Zealand).

There are several different combinations of virus strains in commercial vaccines. The natural antigenic drift means that vaccination is not likely to confer certain and complete protection. Rather it serves to modify the course and severity of the infection. Vaccines are regularly up-dated to include the most recent strains so that the conferred immunity is as near to the field virus as possible.

Immunity to the adjuvanted vaccines is reported to be around 6–9 months, but the immune-stimulating complex vaccines provide protective antibody for 12–14 months.

Passive immunity is transferred to the foal via the colostrum and is probably protective for up to 6–8 weeks.

Primary vaccination for a foal is instigated at around 5–6 months of age. Vaccination is repeated at 30 and 150 days after the initial vaccination. Annual boosters are usually given, with stud mares receiving a booster some 3–5 weeks pre-term.

Equine herpesvirus 1 and 4 (rhinopneumonitis)

Infection with equine herpesvirus 1 is a serious cause of abortion, neurological disease in adult horses and neonatal death in foals. Vaccination has become more widely used since the quality of protection has improved. Infection with equine herpesvirus 4 is probably less serious but can cause abortion.

The vaccines do not appear to prevent the development of the neurological form of the disease.

There are three types of vaccine available:

Usually three doses are administered at 3–4-week intervals with 6-monthly boosters thereafter, but individual vaccines may have particular requirements for the various classes of stud animals. It should be noted that for maximum protection all in-contact horses must be regularly vaccinated.

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