A female dog is bred for the first time during her second heat cycle or after, provided that she is no older than 12 years of age. A male dog is ready to breed by about 15 months of age.
Female dogs typically begin their first heat cycles at 6 to 8 months of age. For their health, females are not bred during their first heat cycles. Male dogs begin producing sperm at approximately 6 months of age, but they are not sexually mature until between the ages of 12 and 15 months. Female dogs older than 12 years are not used for breeding due to the physical toll that breeding and whelping take.