A cute Havanese puppy looking for a playmate.
Most canine females’ estrous cycles occur more or less twice a year. Exceptions to that rule are found in the Basenji breed and in wolf hybrids. Those animals typically exhibit only one estrous cycle per year. It is interesting to note that the age a female reaches puberty relates to her body size or growth plane, but the length of estrous cycles is not correlated to body size.
Seasonality
Dogs’ fertility (the propensity for normal pregnancy) does not seem to differ in response to its climatic seasonal environment. An extensive study of a number of breeds and cross-bred dogs showed that estrus activity (periods of receptivity of females) were identical in January and July (11.4 percent in each month). A slight reduction of estrus activity was observed in December (10.9 percent), and the rest of the months of the year saw very similar figures (6.4 to 8.3 percent). Seasonal or climatic changes seem to influence the estrous cycles of feral canine populations.
Condition
Other than body size and breed peculiarities, several other factors influence puberty and estrous cycles. Among them are injuries, diseases, nutrition, and the presence of other intact females in the same home or kennel. They are discussed at length in the chapter on breeding problems (Chapter 4).
The general health and fitness of bitches play extremely important roles in their reproductive cycles. Animals exhibiting or recovering from injuries or illnesses may not cycle, or their cycles may be abbreviated or otherwise modified. That is another general rule to which exceptions are frequently noted.
I have seen live, reasonably healthy puppies born to weak, emadated bitches suffering from poor nutrition, complicated by infections, intestinal parasites, fleas, and ticks. High puppy mortality usually accompanies such litters, but dogs have an amazing ability to perpetuate their species in the face of adversity.
A German Shorthaired Pointer relaxing on the sand.
Example: I had occasion to treat a 30-pound mixed breed bitch about eight months old that a client picked up on the roadside of an Arizona Indian reservation. She was emaciated, anemic, weak, dehydrated, and nearly comatose. One femur was fractured with the bone ends overriding each other several inches. Her coat had once been long, but was now sparse due to an active mange infestation. She also harbored three types of intestinal parasites.
Together with general anesthesia and surgical bone repair, she was treated for her various parasite infestations and anemia. Her response to treatment and premium diet was exemplary. On a splint check-up visit two weeks later, I discovered she was about one month pregnant. Spaying her was considered, but her new owners elected to wait until after her other ailments were handled. Due to her stressed condition, I predicted she might not carry the litter to term. Surprise! She uneventfully delivered and raised five nondescript puppies.
Nutrition
Females with nutritional deficits due to starvation, poor-quality food, or unbalanced diets may cycle normally, but they may not conceive when bred. Some conceive but abort or resorb (see Fetal Resorption and Abortion, page 62) embryos early in gestation. The nutritional status of a bitch relates to the quantity and quality of food offered (see Pregnancy Nutrition, page 69) as well as her ability to normally absorb and metabolize the food she eats.
Parasites
Another important aspect of a dog’s general condition is associated with parasite infestation. Animals that are supporting large populations of internal or external parasites are being robbed of nutrition, regardless of the quality and quantity of food consumed (see Health and Immune Status of a Female, page 28).
Obesity
Obese bitches often have erratic estrus cycles as well. Obesity may relate to simple glutinous overeating, eating a high-calorie, unbalanced diet, lack of exercise, or occasionally, endocrine imbalances.
Induced Estrus (Dormitory Effect)
A unique and poorly explained canine estrous idiosyncrasy is often reported in scientific literature without interpretation. It is especially prevalent in kenneled dogs, but may also be seen when two adult, intact females live in the same house.
A bitch in heat influences other intact bitches in the immediate environment to begin proestrus. Sometimes referred to as the dormitory effect, it is studied by a few, denied by many doubters, and affirmed by most of us. Simply put, typical proestrus, followed by normal standing heat may be induced in one female by another bitch in heat.
I doubt that anyone fully understands the mechanism of induced estrus, but some experts believe that it may be due to pheromones that are produced by bitches in the proestrus or estrus phase of the estrous cycle. (Pheromones are chemical substances produced by one animal that stimulate certain behavioral responses in other animals of the same species.)
Split Heats
False heats, sometimes referred to as “split heats,” are phenomena that often confuse dog breeders as well as veterinarians. Females display outward signs of normal proestrus, then, before breeding times are reached, heat signs disappear. They show no signs of heat for several weeks, then begin normal proestrus followed by standing heat.
I have also heard the term “wolf heat,” used in reference to split heats. The explanation referring to wild canines suggests that female wolves exhibit a few days of proestrus bleeding to signal males that breeding time is approaching. The brief prostrus signs also tend to induce heat in other females, thus setting the stage for breeding male selection and general gathering of the pack for annual reproductive rites.
This Basset and his pal are taking time out for a little belly rubbing and relaxation.
Maturity
A bitch’s sexual maturity relates to puberty, ovulation, acceptance of a male, and conception. If a capable male is present, she will stand and can be bred for several consecutive days during the estrus stage of any normal heat.
Our discussion of the best time to breed your bitch should include more than her willingness or ability to be bred. Unfortunately, bitches that are not confined behind a dogproof fence are sometimes mismated on their first heat. No matter how well trained she is, when left to her own devices, the influence of hormones and inherent desire to perpetuate the species take precedence over all else.
At what age should a bitch be bred? All generalities are dangerous. One often hears that no dog should be bred until her second heat, or until she is one year old. That implies that all dogs mature at the same rate and by the same age. Alas, that is not the case at all. Sometimes individuals of all breeds are very immature at one year of age, and should not be bred until they are much older. Others may not reach puberty
