UNP-0052 Canine Breeding and Reproduction
UNP-0052, Updated December 2008.
Julio E. Correa, Extension Animal
Scientist, Associate Professor, Food
and Animal Sciences, Alabama A&M University.
Canine Breeding and
Reproduction |
Introduction
Allowing the female dog (bitch) to have puppies
can be a wonderful experience. However, dog owners must understand
the responsibility that comes with breeding since overpopulation
is a tremendous problem. There are too many abandoned and unwanted
mixed and purebred dogs in pounds and shelters all across the
country that have to be euthanized (put to sleep) each year. Unless
every newborn puppy is guaranteed a loving home, dogs should be
spayed or neutered before they reach sexual maturity (6 to 16
months of age, depending on size and breed).
Factors to Consider Before Breeding
- Availability of Good Homes. Owners should identify loving homes for puppies before
breeding decisions are made.
- Health Status. Prior
to breeding, the bitch and the male dog should be in good physical
condition. Dogs should have up-to-date vaccinations and be free
of diseases and physical abnormalities, including healthy reproductive
tracts. A canine brucellosis test should also be conducted before
breeding occurs, even if it is an uncommon disease among dogs.
- Hereditary Disorders. Clearances from any hereditary disorders that are
common to the dog's breed (e.g. canine hip dysplasia) should
be obtained before breeding.
- Behavioral Problems. Both the bitch and the male dog must be of sound temperament.
- Registration.
Both dogs should be registered with a national kennel club, especially
if the puppies are going to be registered before they are sold.
The Reproductive Tract of the Bitch
- Ovaries. These
organs produce ova (eggs) and certain reproductive hormones.
The eggs in the ovaries develop within fluid-filled sacs called
follicles.
- Oviducts. These
tubes move the ovulated and released eggs from the ovaries to
the uterus in approximately two days. Moreover, the oviducts
are the sites of egg maturation and fertilization.
- Uterus. This
organ consists of two long horns and a short body. The uterus
is the site of implantation and placental and fetal development.
- Cervix. This
structure is a constricted orifice that serves as a channel from
the uterus to the vagina. During pregnancy the cervix closes
the birth canal and serves as a barrier against the entry of
microorganisms into the uterus.
- Vagina. This
hollow organ extends from the cervix to the vulva. The inner
lining of the vagina is made up of cells that undergo particular
changes during the estrous cycle.
- Vulva. This
structure is composed of the external genitalia, which includes
the clitoris (sexual organ) and two vertical lips.
The Reproductive Tract of the Male Dog
- Testicles.
These masses of seminiferous tubules are responsible for the
production of sperm cells and the male sex hormone testosterone.
Cells lining the seminiferous tubules produce sperm, while cells
found between the semini-ferous tubules produce testosterone.
- Epididymis. These
ductules are the sites of sperm maturation.
- Vas Deferens. This
is the ejaculatory sperm duct that is also called ductus deferens.
- Prostate. This
accessory sex gland is responsible for the production of the
fluid portion of the semen.
- Urethra. This
hollow tube originates at the neck of the bladder and runs through
the penis to transport urine. During mating, it transports semen.
- Penis. The
dog's penis contains two rather unique characteristics:
- Os Penis. The
objective of this small bone within the free extremity of the
penis (glans penis) is to direct the male's non-erect penis into
the bitch's vulva and vagina during the early stages of mating.
- Bulbus Glandis. This
swelling of the penis is located toward the rear end of the os
penis. As soon as the male dog inserts his penis into the bitch's
vagina and begins to thrust, the bulbus glandis enlarges to a
firm spherical shape, resulting in the so-called "coital
tie." This tie prevents the male dog and the bitch from
separating immediately after ejaculation and may last from 5
to 60 minutes.
- Prepuce. This
foreskin or outer covering is where the external opening of the
penis usually lies.
- Scrotum. This
sac of skin is where the testicles are suspended outside of the
peritoneal cavity.
The Estrous Cycle of the Bitch
Bitches become sexually mature when they exhibit
their first heat period, usually between 6 and 16 months of age,
depending on the size and breed. Most bitches come into heat twice
a year. The exceptions to this rule are wolves and basenjis, which
typically exhibit only one heat cycle per year. The estrous or
heat cycle of an intact (unspayed) and nonpregnant bitch is divided
into four separate phases:
- Proestrus. The
most reliable indicator of the beginning of this phase is the
bloody vaginal discharge. This bloody discharge is due to the
leaking of red blood cells from capillary vessels lining the
uterus into the lumen of the uterus. Other indicators are swelling
of the vulva and frequent licking of the external genitalia.
During proestrus the bitch will attract male dogs but will not
allow mounting or mating. Proestrus usually lasts between 6 to
11 days, but generally lasts for nine days. During this phase
the follicle-stimulating hormone (FSH) and the luteinizing hormone
(LH), both secreted by the pituitary gland, stimulate growth
and development of follicles within the ovaries. Furthermore,
the levels of the hormone estrogen, which is primarily produced
by the follicles, rise gradually in the bloodstream causing behavioral
estrus in the bitch.
- Estrus. This
phase begins when the bitch allows mounting or mating. To indicate
sexual receptivity, the bitch crouches, elevates the rear quarters
toward the male and moves the tail to one side. During this phase
the vaginal discharge becomes a straw or light pink color. The
average duration of estrus is about nine days, but it can last
from 2 to 21 days. During this phase estrogen levels decrease
and progesterone levels increase. Furthermore, it is during estrus
that ovulation (release of eggs from ovarian follicles) takes
place. A surge in LH from the pituitary gland triggers ovulation,
which occurs 1 to 3 days after LH levels peak in the bitch's
bloodstream. All mature ovarian follicles rupture and release
their eggs into the oviducts within 24 to 48 hours. Generally,
larger dog breeds ovulate more eggs than smaller breeds. Released
eggs undergo maturation in 2 to 3 days and remain viable for
a period of 12 to 72 hours. Following ovulation, each ruptured
follicle changes to corpus luteum, a yellow body responsible
for increasing progesterone levels during estrus. It is worth
mentioning at this point that extreme care must be taken during
the estrus phase in order to prevent unwanted pregnancies. The
bitch must be supervised when she is allowed to go out into the
yard or taken out for walks.
- Diestrus. This
phase, which lasts about two months, begins with the bitch becoming
unattractive to the male dog and lasts until the corpora lutea
(plural of corpus luteum) regresses. Hence, diestrus is under
the influence of the hormone progesterone. If the bitch has been
bred, this phase is the beginning of pregnancy. However, whether
or not the bitch has been bred and becomes pregnant, the corpora
lutea are maintained and remain functional, secreting progesterone,
which is important for the maintenance of pregnancy.
- Anestrus. This
phase is considered to be a quiet rest stage in the estrous cycle.
Factors such as breed, age, size, and health condition will influence
the duration of anestrus. The length of anestrus varies, lasting
on average about 3 to 5 months. During this phase, the bitch
shows no signs of heat and no sexual interest in males. Following
anestrus, the heat cycle begins again.
The Reproductive Cycle of the Male Dog
Male dogs, like bitches, reach sexual maturity
at varying ages, depending on the size and breed of the dog. Most
males are sexually mature and capable of producing sperm at about
10 months of age. The hormones FSH and LH, secreted by the pituitary
gland, stimulate the production of sperm (spermatogenesis) and
testosterone by the testicles. Testosterone is necessary for the
development and maintenance of male sex characteristics, male
sexual behavior, and spermatogenesis, which occurs throughout
the year and lasts for a period of 62 days.
Mating
The best rule to follow when breeding dogs
is to be certain that they are physically mature. This means that
both the bitch and the male dog should be 18 to 24 months of age,
by which time the bitch should be in her second or third heat
period. Since ovulation usually occurs on the second day of estrus,
it is highly effective to breed the bitch as soon as she is sexually
receptive to the male dog and again two days later.
The bitch is usually brought to the male dog
for breeding. Courtship behavior begins with the male dog sniffing
at the bitch's face and flank and licking of the vulva. When ready,
the bitch presents her hindquarters to the male dog and stands
still with her tail toward one side. The male dog then clasps
the flanks of the bitch with his forelegs, inserts his penis into
the vagina (intromission) and begins to thrust. The enlargement
of the bulbus glandis occurs at this time, resulting in the coital
tie. With the penis firmly in place, ejaculation begins. Then
with their genitalia still "locked," the male dog will
dismount by placing both front feet to one side and lifting one
hind leg over the bitch's back so that they are facing in opposite
directions. The enlarged bulbus glandis of the male dog prevents
separation from the bitch for about 5 to 60 minutes. Do not interfere
with a coital tie as injury could result. Separation occurs naturally
and both dogs usually wash themselves afterwards.
When artificial insemination (AI) is properly
performed, conception rates are equal to those attained by natural
breeding. However, the American Kennel Club (AKC) has regulations
concerning the registration of dogs produced by AI. Therefore,
before using this technique, check with the AKC or the local kennel
club for information about AI and registration of puppies.
Pregnancy
The pregnancy or gestation period extends from
the time of successful mating to parturition. Sperm cells will
reach the eggs in the oviducts of the bitch within 30 seconds
of ejaculation and have a viable life span up to seven days. Fertilization
(union of sperm and egg) takes place in the distal portion of
the oviducts and occurs a few days after mating.
The resulting zygotes (fertilized eggs) begin
cell division growth, and the growing organisms are then called
embryos. The developing embryos move from the oviducts into the
uterus 6 to 10 days after conception and implant or attach to
the uterine walls 17 to 21 days after fertilization. As they implant
and their placenta develops, the embryos are then called fetuses.
The fetuses are usually evenly spaced throughout the two uterine
horns.
The pregnancy or gestation period of the bitch
lasts between 56 to 66 days, with an average length of 63 days.
As mentioned previously, during this period the corpora lutea
are maintained and remain functional, secreting progesterone,
which is important for the maintenance of pregnancy. To confirm
pregnancy, palpation of the bitch's abdomen for the presence of
evenly spaced swellings can be conducted by an experienced person
between 20 and 30 days after the last mating. However, improper
procedure or excessive prodding can cause a miscarriage. After
confirming that the bitch is pregnant, make sure you become familiar
with the basics of prenatal care, parturition (whelping), and
emergency procedures.
A pregnant bitch requires additional food to
support the growth of pups inside her and to produce the milk
that pups will need after birth. Feed her the same amount of the
usual adult maintenance diet for the first 4 weeks of pregnancy.
Then gradually increase the amount of food so that by whelping
time she is eating about one and one-half times her maintenance
diet. Consider switching to a commercial dog food that is specifically
formulated for pregnancy and lactation. However, due to possible
whelping problems, make sure that the bitch does not gain any
excessive weight during this period.
Very few physical changes occur until the fifth
week of pregnancy. By the fifth week of pregnancy, the nipples
and mammary glands swell and darken in color. Between the sixth
and seventh week, the bitch's abdomen is enlarged due to the growth
of the pups. At about 8 weeks into the pregnancy, the bitch's
mammary glands will enlarge considerably and milk may appear on
the nipples.
Whelping
About a week before the estimated date of parturition,
the bitch should be introduced to the whelping area and the whelping
box. The whelping area should be a place that is dry, warm, draft-free,
secluded, and quiet. The whelping or nesting box may be constructed
of a variety of materials but should be designed to accommodate
the bitch fully stretched out on her side and have room to spare
for the pups. The bitch should be able to step into it, but the
pups should not be able to climb out. The whelping box should
include an interior shelf around the periphery to prevent the
bitch from smothering or crushing a puppy. This shelf should be
high enough to accommodate a puppy, but low enough to prevent
the bitch from stepping or rolling on a puppy. The bedding of
the box should include fresh, flat newspaper laid at the bottom
for fluid absorption and heavy towels, mattress pads, or pieces
of carpeting laid on top of the newspaper for good traction.
If necessary, a source of supplemental heat
should be placed in the whelping box for the puppies, especially
after the first few weeks of birth. Supplemental heat can be furnished
by using heat bulbs either suspended or mounted above the floor
of the whelping box. However, make sure to leave an mental heat,
so the bitch and puppies can move away from the heat if they get
too hot.
The whelping process usually does not require
assistance. However, for emergency purposes, the following supplies
should be kept on hand:
- A clean, small plastic syringe to aspirate
secretions from the mouth and nose.
- A spool of dental floss to tie the umbilical
cords.
- A pair of sterilized, straight, blunt-tipped
scissors, in case it becomes necessary to cut the umbilical cords.
- A small bottle of iodine solution to apply
to the umbilical cords.
- Several clean, laundered towels for drying
the puppies.
Approximately 12 to 24 hours before labor begins,
the rectal temperature drops from a normal of 101.5 degrees F
(38.6 degrees C) to less than 100 degrees F (37.7degrees C). In
addition, the bitch loses her appetite, becomes restless and lethargic,
and her abdomen becomes more distended. An increase in the production
and secretion of the hormone prostaglandin F-2-alpha by the placenta
and uterus causes regression of the corpora lutea and a subsequent
decrease in progesterone. The decrease in progesterone permits
uterine contractions to occur. The hormone relaxin is important
for the preparation of the uterus for parturition and the separation
of the pubic bones for passage of the puppies through the birth
canal.
The labor and delivery process in dogs usually
does not require human intervention, and it entails three stages.
- Stage I, which
lasts about 6 to 12 hours, is characterized by mild uterine contractions
and dilation of the cervix. At this time the bitch displays external
signs such as intense nesting and constant lying down and standing
up.
- Stage II is
characterized by intense uterine contractions, which causes the
expulsion of the puppy. Bitches usually deliver lying down, but
some may assume a squatting position. Most puppies are born with
feet and head first. The bitch should instinctively start to
lick the fetal membranes away from the puppy's face, and then
sever the umbilical cord with her teeth. There should be no interference
with this maternal process. However, if the bitch does not act,
you should step in and break the membrane with your fingers,
so the puppy can breathe. Similarly, the umbilical cord needs
to be tied, cut, and disinfected with iodine.
- Stage III is
characterized by expulsion of the placenta. The bitch usually
expels a placenta within a few minutes after the expulsion of
each puppy. It is normal and instinctive for the bitch to eat
the placentae. However, you may want to reach and take some of
them from her to avoid undesirable adverse effects. Make sure
that the bitch has expelled a placenta for each puppy. If she
retains any, she may develop postpartum metritis and need veterinary
help. In general, the bitch will deliver her entire litter over
a period of several hours. The uterus usually returns to its
normal size (involution) within 12 weeks of whelping.
Postpartum and Postnatal Care
Since the bitch's appetite returns within 24
hours after whelping, she should be fed a highly palatable food,
moistened with water. Furthermore, at about 20 to 30 days after
whelping, the bitch needs three to four times more food than she
normally does. Although the eyelids of the puppies are not open
at birth, they can still locate the bitch's nipples in order to
feed. This is of extreme importance since the puppies must consume
colostrum (dam's first milk) within the first 12 to 24 hours after
birth. Colostrum contains high levels of antibodies that are absorbed
intact into the bloodstream and provide protection against infectious
diseases. Hence, make sure that each puppy has access to a nipple
and is able to suckle. Remember that the most important indicator
of puppy health during the first few days and weeks of life is
regular and normal weight gain. If a puppy does not gain weight
during the first 72 hours of life, you should start supplemental
feeding immediately. Commercial milk formulas, which can be obtained
from pet supply stores, should be fed warm in a small bottle with
a hole in the nipple.
Handle the puppies daily to get them used to
human contact, and change the bedding often to prevent urine burn.
As you handle them, inspect for cleft palates, umbilical hernias,
Atresia ani (absence of an anal opening), and any other abnormal
conditions.
At about three weeks of age, puppies should
be given access to dry dog food mixed with warm water (gruel)
in a large bowl several times a day. Gradually, the water content
should be reduced so that by 4 to 6 weeks of age the puppies are
meeting most of their requirements with the dry food. By this
time there is less demand on the bitch's milk, and her food intake
should be reduced. This initiates the process of stopping milk
production and helps to normalize the bitch's food intake. After
about 6 or 7 weeks of age, puppies are ready to be weaned and
placed into new homes. Before sending them off, make sure they
have been treated for parasites and vaccinated for distemper,
hepatitis, leptospirosis, parvovirus, coronavirus, and kennel
cough.
Some Common Reproductive Problems
- Silent Heat. This
term refers to a bitch that is in estrus but is not exhibiting
vulvar swelling and vaginal bleeding.
- Prolonged Heat.
This term refers to a bitch that remains in estrus for more than
21 days. This condition is usually the result of excessive levels
of estrogen due to ovarian tumors or follicular cysts.
- Vaginitis. This
infectious disease occurs when pathogenic bacteria invade the
vagina and cause infection.
- Pyometra. This
disease occurs when the uterus has been under the sustained effect
of high levels of pro-gesterone and ideal conditions for bacterial
growth.
- Cryptorchidism.
This inherited trait is the failure of one or both testicles
to descend. Dogs with neither testicle descended are sterile.
- Orchitis. This
is an infection of the testicles.
- Balanoposthitis. This
is an infection of both the penis and prepuce.
- False Pregnancy. This
condition refers to a nonpregnant bitch acting as if she was
pregnant. The condition is caused by progesterone produced by
corpora luteal cysts in the ovaries.
- Dystocia. This
term refers to prolonged or difficult labor caused by a physical
blockage or uterine inertia.
- Mastitis. This
term refers to an infection and inflammation of the bitch's mammary
glands (normally five pairs).
- Brucellosis. This
disease, which is caused by the bacterium Brucella canis, is
a well-recognized cause of abortions and stillbirths.
Conclusion
It is advantageous to have knowledge of canine
reproductive anatomy and physiology, the estrous cycle of the
bitch, mating, pregnancy, whelping, and postnatal care of pups
if you are planning to breed dogs. Furthermore, your objective
should be to improve the standard of the breed. Remember, pounds
and shelters all across this country are already full of unwanted
dogs.
References
Case, L.P. (1999). The Dog: Its Behavior,
Nutrition, and Health. Ames, Iowa: Iowa State University Press.
Currie, W.B. (1988). Structure and Function
of Domestic Animals. Stoneham, MA: Butterworth
Publishers.
Giffin, J.M. and L. Carlson. (2000). Dog
Owner's Home Veterinary Handbook. New York, NY: Hungry Minds,
Incorporated.
Marder, A. (1997). The Iams Company Complete
Dog Owner's Manual. Australia: Weldon Owen Private Limited
Company.
Pond, W.G. and K.R. Pond. (2000). Introduction
to Animal Science. New York, NY: John Wiley & Sons, Incorporated.
Rice, D. (1996). The Complete Book of Dog
Breeding. Hauppauge, NY: Barron's Educational Series.
Whitehead, S. (1999). Dog: The Complete
Guide. London, UK: Team Media, Limited.
For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information.
Issued in furtherance of Cooperative Extension work in agriculture and
home economics, Acts of May 8 and June 30, 1914, and other related
acts, in cooperation with the U.S. Department of Agriculture. The Alabama
Cooperative Extension System (Alabama A&M University and Auburn
University) offers educational programs, materials, and equal
opportunity employment to all people without regard to race, color,
national origin, religion, sex, age, veteran status, or disability.
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