Breeding of pet dogs can be done either naturally or by artificial insemination. Fresh semen, or frozen semen after thawing, can be used to artificially inseminate the female dog. For natural breeding, the male and female dogs are brought together, preferably in the home of the male, as breeding is generally more successful when the male dog is in an environment familiar to it. However, since there’s a surplus of dogs in almost all countries around the world, casual breeding of dogs is not a good idea.
For successful breeding, the female dog has to be in estrus. This fertile period of the female dog usually occurs twice a year, but it can be anywhere from 4 months to a year apart. The females typically have four phases in their reproductive cycle. During the anestrus phase, the ovaries of the dog are inactive, and the uterus remains small in size. A female dog in the anestrus phase will not allow the male to mount it. Male dogs are not naturally attracted to an anestrus female either. Towards the end of the anestrus phase, the production of female reproductive hormones such as the follicle stimulating hormone and the luteinizing hormone are increased, leading to the proestrus phase.
Females in the proestrus phase can be recognized by their enlarged vulva and the discharge that comes from the vagina. The estrogen levels in their blood increase, but they still do not allow mating even though they are attractive to the male counterparts at this time. The proestrus stage in dogs is usually about 9 days in duration, after which the females become estrus.
Females in estrus are in their fertile phase, and they are receptive to males and allow mating during this period. The estrogen levels in their blood decrease at this time, and the levels of progesterone hormone increase. Estrus phase in the female usually lasts 9 days, but variations occur, with some dogs being in estrus for just 3 days, while others remaining reproductive for up to 3 weeks.
The final phase is the diestrus phase in which the female does not allow to mate again. The discharge from the vagina becomes less, but the uterus gets enlarged under the influence of progesterone. The diestrus phase is about 2-3 months in duration. The progesterone level remains high in the first half of it, and if the dog is not pregnant, it starts to decline gradually. But if the mating has been successful, the progesterone level continues to be high throughout the period of gestation, which is about 65 days in dogs.
The estrus cycle of some domestic animals may be manipulated, but this is difficult in dogs. Female dogs have to be spayed for preventing estrus permanently, but it can be suppressed temporarily by administering drugs. But these drugs are known to cause certain changes in the liver and the skin in addition to vaginal inflammation. When the female is in the anestrus phase, certain drugs can be used to speed up the transition to the estrus phase, if required.
Unplanned mating and resultant pregnancies in pet dogs can be a problem because of the possible complications related to pregnancy and delivery. The permanent solution to this problem is neutering and spaying. If a pregnancy is unwanted, the veterinarian may administer prostaglandin F2alpha hormone to terminate it. A corticosteroid drug called dexamethasone may be used instead.