a "birth certificate"; a foal that does not meet the breed standards may be denied registration even if both parents are registered Aztecas approved for breeding. Full registration and approval for breeding are subject to a second and more detailed inspection at age three or more, and granted only to those horses that fully satisfy the requirements of the standard. In the American Azteca registry, horses with American Paint Horse (APHA) breeding are also allowed. However, horses with more than 25 percent Thoroughbred blood in their pedigrees (common in many Paints and Quarter Horses) within four generations cannot be registered. American Aztecas have four categories of registration based on the relative degree of blood from each foundation breed, seeking an ideal blend of 3/8 Quarter Horse and 5/8 Andalusian. Unlike their Mexican counterparts, they do not have to go through physical inspections before being registered. History The Azteca was first bred in 1972 as a horse for charros, the traditional horsemen of Mexico. Antonio Ariza Cañadilla, along with others, was instrumental in the creation of the Azteca horse as the national horse of Mexico and with its official recognition by the Mexican Department of Agriculture on November 4, 1982. Ariza used imported Andalusians, crossed with Quarter Horses and Criollos and began to breed the foundation horses of the Azteca breed at Rancho San Antonio near Texcoco, Mexico. Early in the Azteca's history, breeders realized the need for a unified breeding program in order to produce horses that met the required characteristics. The Azteca Horse Research Center was created at Lake Texcoco, and in partnership with breeders developed the phenotype of the breed today. The first official Azteca was a stallion named Casarejo, who was a cross between an Andalusian stallion named Ocultado and a Quarter Horse mare named Americana. He was foaled at the Centro de Reproduccion Caballar Domecq in 1972. The Associacion Mexicana de Criadores de Caballos de Raza Azteca, or Mexican Breeders Association for the Azteca Horse, is the original breed registry and still maintains the international registry. The International Azteca Horse Association and its regional affiliates was formed in 1992. The majority of Aztecas are found in Mexico, and the Mexican association had registered between 10,000 and 15,000 horses as of 2005, according to the Texas Department of Agriculture. The Mexican registry adds approximately 1,000 horses per year. The Azteca Horse Registry of America was formed in