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Reproduction in Dogs

Picture of a family of dogs

Though most pet owners prefer to spay and neuter their dogs, many are interested in better understanding the female dog’s heat cycle. Contrary to popular belief, a female dog is not fertile all the time. Much like the female dog’s human counterpart, she will experience menstrual seasons known as “heats” in canine terminology, and only during specific times in this heat cycle is she primed to conceive. However, unlike in women, a female dog will typically undergo a season a maximum of two times yearly. These heat cycles most commonly last a maximum of 30 days and occur approximately six months apart from each other. Though pregnancy typically occurs only during what is known as the standing heat phase, it is possible for a female to conceive at any time during her cycle, and thus, total separation from male dogs for the entirety of the heat is recommended.

The Stages of a Heat Cycle

When a family obtains a female dog as a puppy, there is a period of respite from heat cycles while the puppy is yet sexually immature. When the puppy enters puberty, she will experience her first heat. Though technically a female dog may be capable of conceiving and whelping puppies as early as six months of age, she physically and emotionally is not ready. Breeding this young is in the best interest of no one; certainly not the mother dog and her puppies. Most reputable breeders defer breeding a female until she has reached two years of age and has successfully passed all required health testing. These two measures ensure the health and well-being of the female dog in question as well as the future of any litters she may bear.

A dog’s first heat will appear at different times for different breeds and even at different times for different dogs within the same litter. As a general rule, smaller breed dogs will undergo their first cycle much sooner than larger breeds. Heat cycles can occur as early as six months or even as late as 18 months; it is a highly individual biological process.

The female dog’s heat cycle is characterized by specific stages.  They are as follows:

  • Proestrus
  • Oestrus
  • Diestus
  • Anestrus

 The Proestrus Phase

The proestrus period is the prelude to the heat cycle. During this time period which typically lasts nine days, a female dog’s eggs are reaching full maturity and will soon move into the proper position to be released. As estrogen levels begin to rise, the dog’s vulva will gradually swell, and there is often the appearance of blood droplets from this region.

During the proestrus stage, the female dog will begin to emit a fragrance which will attract male dogs. Many may attempt to become amorous with her, but a female dog will not accept a male’s advances until she is ready to conceive. Most commonly, she will rebuff any romantic overtures from a male dog during this period.

Since hormones are running quite high even during the proestrus phase, it is important for the bitch to be kept behind locked doors, safely away from any potential suitors. Equally as important is the separation of same sex intact animals to prevent any fighting amongst dogs who may want to compete for the affections of the female dog.

Other common signs that indicate a heat cycle are swollen nipples, moodiness, and excessive clinginess to the owner or other family members.

The Oestrus Phase

The oestrus phase, which also can run approximately eight days, is the time period when the female is ready to mate. The eggs typically begin their descent from the ovaries beginning on Day 10. While estrogen levels begin to decrease, testosterone is on the upclimb!

During this phase, the female will actively flirt to attract male attention. One of the most commonly recognized signs that a female has entered the oestrus stage is the flagging of her tail. Flagging is evidenced by the female moving her vulva directly into the face of a male while moving her tail to the side. This is intended to alert the male dog to her fragrance which is evidence that it is prime breeding time.

For some females, the oestrus period marks a time when the previous bloody discharge suddenly becomes clear.

The oestrus phase is the optimal time for breeding to occur. Though females can become pregnant in the proestrus phase and even into the diestrus, it is far less likely. Precautions should be maintained during all stages of a heat cycle, but to have the greatest chance of a viable pregnancy, reputable breeders aim for a first breeding on Day 10, then breeding every other day until the male loses interest or the female will no longer “stand” for the male. When either (or both) of these things occur, it is a clear sign that the oestrus portion of the heat cycle has been completed.

It is interesting to note that even if the first breeding attempt was successful that both dogs will continue to be interested in repeated breedings until the bitch is no longer in standing heat. Since semen lives up to 48 hours in the uterus and eggs are just beginning to be released on Day 10, it is entirely possible that the first breeding will not be successful. For this reason, reputable breeders prefer several mating attempts to just one.

The Diestrus Phase

The diestrus phase occurs whether a breeding attempt has been successful or not. However, the changes to a bitch’s body will be different according to which state she finds herself in. If a mating results in a pregnancy, there is a 63 day gestation period from the date of the successful conception. With multiple breeding attempts, it can be difficult to ascertain precisely which one was the winner. Breeders most commonly count 63 days from the earliest possible successful breeding attempt and mark that on their calendars as a potential whelp date. Sometimes the bitch will go into whelp a little earlier; sometimes, it will be later. But this is an excellent baseline measure to help the breeder to prepare for the imminent arrival of puppies. During the diestrus period; whether pregnant or not, a female will no longer receive the attention of an interested male party.

If no breeding was attempted or a breeding attempt was not fruitful, the diestrus period will last from 60-90 days. It is highly recommended if a bitch is not used for breeding that she be spayed as every heat cycle a female is not bred, she runs an exceptionally high risk of developing pyometra. Pyometra is a life threatening condition. Essentially, the uterus becomes infected and expands to fill with pus and bacteria. The poisons in the body begin to invade the bloodstream and can also lead to a uterine rupture. Pyometra, unless caught in time, is typically fatal. Pyometra can also affect bitches used in a breeding program, but there is no reason to assume this unnecessary risk in a dog intended only to live the happy life of a house pet.

The Anestrus Phase

Simply put, the anestrus phase is the time frame from one heat cycle until the next. Most commonly, it lasts between four to five months.

With pet overpopulation a leading problem in our country today, many wisely feel that breeding is best left in the hands of experienced and reputable breeders. But each owner with a female dog will experience at least one heat cycle prior to a spay, so it is good to be prepared for what lies ahead by knowing all of the facts ahead of time.

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