Dogs are fertile when they come into heat at 7 or 8 months, but the second heat is a better time to give birth. The sexual maturity of the creature precedes the physical maturity, and it is better to have a litter after the physical maturity. A dog’s life span is between 12-14 years, and their optimal age for fertility is 2-3 years, which is equivalent to a person’s 20s or 30s. Dogs to 8-10 years old, that is, people from middle age into old age period, when fertility began to weaken, but not yet completely lost.
