Chihuahua (dog) The affected chihuahua will hold its leg flexed, and foot off the ground until the quadriceps muscle relaxes and lengthens, after which the animal feels no discomfort and continues with activity. Chihuahuas are also prone to some heart-related disorders, such as heart murmurs and pulmonic stenosis, a condition in which the blood outflow from the heart's right ventricle is obstructed at the pulmonic valve. Chihuahua (dog) The Chihuahua () is the smallest breed of dog and is named after the state of Chihuahua in Mexico. Chihuahuas come in a wide variety of colors, and two coat lengths. The Chihuahua's history
Dog breed in 1873 in imitation of other stud book registries for cattle and horses. Ancient breed of dogs was a term once used for a group of dog breeds by the American Kennel Club, but no longer. These breeds were referred to as "ancient breeds", as opposed to modern breeds because historically it was believed that they had origins dating back over 500 years. In 2004, a study looked at the microsatellites of 414 purebred dogs representing 85 breeds. The study found that dog breeds were so genetically distinct that 99% of individual dogs could be correctly assigned to their breed