Females of most breeds of domestic dogs will show their first heat (or estrus) period before they are a year old and sometimes before six months. There are considerable variation both between breeds and individuals. Most domestic breeds come into heat at any season of the year, at approximately six months intervals. The pattern of any individual dog is usually fairly consistent, but longer and shorter cycles are common.
"Heat" or "season" is the term used to describe the time when the female dog will mate. It is during this period that pregnancy may occur. Each heat last approximately eighteen days.
A bitch's first season usually occurs when she is between six and nine months old. Bitches are capable of conceiving throughout their lives. They are never too old to have a litter and come into heat twice a year. This cyclic progression is interrupted only by pregnancy.
The first sign of heat in the female is a gradual enlargement of the external genitalia, followed after several days by the discharge of a small amount of blood. At the same time an odorous substance highly exciting to males is secreted in the urine. If the female is allowed to urinate where males can find it, males will gather from miles around. Bleeding may continue for a week or more and at its end the female will accept the male to mate. She maybe receptive for a few days or as much as two weeks.
First Stage of Heat
1) During the first stage the bitch's vulva swells noticeable and will have a blood tinged discharge.
2) The bitch becomes attractive to male dogs but she will not be interested in mating.
3) Her appetite and drinking habits may become capricious.
4) This stage last about nine days after the signs of heat first appeared.
Second Stage of Heat
1) During this stage the bitch is capable of conceiving.
2) The discharge from the vulva is straw-colored and free from blood.
3) She will readily accept any dog to mate.
4) She develops wanderlust and , if allowed, will stray from home in the company of male followers.
An owner who wishes to breed from his bitch should attempt to ensure that her mating with the stud occurs as soon as possible after the bleeding stops. Successful breeding is most likely to occur ten to twelve days after the beginning of heat.
After mating, the stud and bitch will remain "tied" together for twenty minutes or so. Separating them forcefully can cause an uncontrollable hemorrhage of the dog's penis, as well as inflict appreciable damage to the vagina. When tied together after mating, leave the dogs for as long as they like. They will separate from each other after some minutes.
Ovulation occurs 72 hours before the last point of receptivity. Conception may occur from mating at any time in the cycle but for maximum fertility the mating should be repeated frequently in order to strike the period of ovulation. Many breeders make a practice of repeating mating every other day throughout the receptive period.
The period is approximately 9 weeks counting from the time when the animal is first receptive. The embryos develop quite slowly at first, not becoming implanted until about 21 days after fertilization. The greatest intrauterine growth of the puppies occurs in the last half of pregnancy, during which the female will require an increased and well balanced diet. Occasionally a female that has not been bred will show a pseudo pregnancy, with swelling of the abdomen and enlargement of the mammary glands.
Litter size varies roughly with the size of the breed, but there is great individual variation. Some toy breeds rarely have more than one or two puppies, whereas the setters and larger breeds may have eight to ten, with some record litters going much higher. Four to six is a good average; in very large litters the pups are frequently small and weak.
The reproductive powers of females diminish after five year of age and reproductive cycles usually cease entirely by the age of eight. males usually remain capable of breeding to a more advanced age, but a male of six years is entering middle age.
Spaying the female (removing the ovaries) or castrating a male (removing the testes) before maturity affect the normal pattern of growth; such animals become taller and more obese than the average. Spaying terminates the cycles in the female, but castration may have little effect on the sexual behavior of an experienced male.
Signs of Approaching Birth
Generally, birth occurs sixty-three days after conception, though on occasion a bitch may give birth a week early or a week late.
1) Approximately six hours before birth, the mother becomes restless and begins bed making, preparing a place to give birth in usually the more convenient places.
2) Vomiting may occur.
3) The animal's body temperature drops by three degrees to about 98 deg F (36 deg C).
4) The vulva becomes enlarged and pinkish.
Various Stages of Labor
1) Within an hour before birth, the mother grows increasingly nervous, and may start glancing at her flanks. There are occasional contractions of the abdomen one contraction every ten minutes, becoming more frequent.
2) The bitch lies down as the contractions become more frequent. As the fetus enters the pelvis, there is definite straining. The water bag, which looks like a black grape, appears at the vulva.
3) The mother will lick the water bag to rupture it. After the water breaks, the nose and feet of the puppy will appear protruding from the vulva.
4) After the violent expulsive effort by the mother, the infant dog is born. Often the mother will yelp or cry out as the puppy's head comes through.