Organizations and registration requirements
There are two registries in the United States for Miniature Horses, the American Miniature Horse Association (AMHA) and the American Miniature Horse Registry (AMHR).
The AMHA was founded in 1978 and was dedicated to establishing the Miniature horse as a distinct breed of horse. The AMHR is a division of the American Shetland pony Club and was established as a separate registry in 1972. In the AMHA, Miniatures cannot exceed 34 inches at the withers (which the AMHA defines as located at the last hair of the mane). There are two divisions in AMHR - the "A" division for horses 34 inches (86 cm) and under, and the "B" division for horses 34 to 38 inches (86 to 97 cm).
Worldwide, there are dozens of miniature horse registries. Some organizations emphasize breeding of miniatures with horse characteristics, others encourage minis to retain pony characteristics.
The AMHA standard suggests that if a person were to see a photograph of a miniature horse, without any size reference, it would be identical in characteristics, conformation, and proportion to a full-sized horse.
According to the AMHR, a "Miniature should be a small, sound, well-balanced horse and should give the impression of strength, agility and alertness. A Miniature should be eager and friendly but not skittish in disposition."
Miniature Horse Club Great Britain (MHCGB) is able to register and issue passports to miniature horses with 50% or more American blood, at least one parent must be registered with the AMHA. This is the only club in the UK to be sanctioned by the AMHA.