the rare Mexican breed, the Xoloitzcuintle and the Chihuahua breed each live very long but im not sure which one lives the longest. soz
beagle
Probably the bull mastiff
A dachshund is a pure breed, not a mix, and one of the oldest dog breeds there is.
The oldest breed of a beagle would be 46 years old
The oldest North American dog breed is believed to be the Alaskan Malamute, which is a breed that was developed by the native Inuit people in Alaska for sled pulling and hunting. It is a strong and resilient breed known for its ability to withstand harsh Arctic conditions.
The oldest breed of domestic dog is believed to be a close relative to the greyhound and Pharaoh hound.
Afgnew Hound :)
The oldest dog breed in Asia is the Shar-pei. This was a fierce breed bred for hunting and guarding. The almost went extinct but due to a population surge in the US in the 1970's the breed has made a remarkable come back.
If you are trying to breed a dog then it should be at least 3 years old, so it is an adult and ready to breed.
You need to specify what breed the dog is in order to get an accurate answer.
Terrier
Do not breed dogs under 3lbs! It is life threatening for the dog!