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REPRODUCTIVE
HEALTH OF THE BITCH
submitted with permission by Marj Brooks
with thanks to Kevin & Donna Frizzell of DeSaix St. Bernards for
generously allowing us to use many of their superb array of articles |
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Generally
speaking, canids are considered to be fertile with approximately 80% of
all bitches mated becoming pregnant in the event of a natural mating.
Conception rates from artificial insemination are again approximately
70 - 80%. Fertility problems do occur: listed below are some steps that
can be taken to reduce this incidence. The links are provided for more
in depth topics regarding the reproductive health of the bitch.
Things
you Can Do to Maximise Fertility in the Bitch:
1) Do not attempt to
breed the bitch until at least 2 years old or after her second season
or after she is six / seven years old as fertility declines and
infections processes increase due to hormonal changes
2) Do not allow your bitch to
become overweight or underweight and ensure that your bitch is in top
physical condition
3) Studies have shown that
Vitamin E given regularly increases chances of improved fertility
4) Ensure that the
reproductive tract of the bitch is clean before mating with routine
swabbing and culture and sensitivities prior to mating +/or during
oestrus
5) Allow your bitch to
rest between litters to reduce the risk of damage to the uterus and
subsequent infertility.
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Pseudo
Pregnancy ~ What Causes It?
A false
pregnancy or pseudo-pregnancy is a normal course of events for a bitch
that has had a season and who is not pregnant. This phenomena occurs
because the Corpus Luteum continues to produce Progesterone which is
the Pregnancy Hormone whether the bitch is pregnant or not. The Corpus
Luteum eventually degenerates at about 49 days if the bitch is not
pregnant. Progesterone production then ceases which is why a false
pregnancy usually resolves itself after the seventh week post oestrus.
The effects of
this on different bitches varies widely but the principles and hormonal
influences from which such behaviours stems remain constant.
Repeated false
pregnancies despite the degree to which the bitch "acts out" these
events do not predispose the bitch to increased risks of Pyometra.
The Bitch May:
develop mammary tissue
produce milk (good indication that the pregnancy is false if there is
milk present 49 days post oestrus)
nest
go into labour and pass small amounts of fluid
adopt and mother toys
mourn for her "lost babies"
become aggressive toward intruders
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The degree to
which the bitch "acts out" the above depends on her individual
personality and disposition rather than a fluctuation in hormonal
events. Whilst it is sad for the bitch it does not warrant radical
treatment as the condition is fairly short lived. Spaying should be
considered as a reasonable option.
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Pyometra
~ Open and Closed
Pyometra is a
potentially life-threatening illness for intact bitches. It usually
occurs about six weeks to two months after the heat cycle because it is
related to the production of progesterone. There are two types of
pyometra:
1) Open Pyometra: This one is easily
detected because it is characterized by a purulent discharge, fever,
anorexia, lethargy and sometimes vomiting.
2) Closed Cervix Pyometra: This more
covert and deadly because there is no discharge but the other signs and
symptoms are present.
The infection
remains within the body and diagnosis is more difficult in that nothing
shows externally. Blood work, radiology, ultrasound and physical
examination are used to rule out other causes before a definite
diagnosis of Closed Cervix Pyometra can be made.
Either type of
Pyometra is life-threatening. Ovario-hysterectomy is regarded by most
veterinarians as the treatment of choice, because even if treated
medically more than 70% of bitches will have recurrent episodes.
However, if it is a valuable brood bitch or at the height of a show
career, owners may wish to postpone spaying until the bitch has had a
litter. In that case, treatment with prostaglandins has proved to be
successful in a majority of cases of open cervix pyometra, but
unsuccessful in a majority of closed cervix cases.
Bitches treated
with prostaglandins should be bred at the next heat in order to
forestall another episode of pyometra which is extremely likely.
Medical
management of closed cervix pyometra is risky and much less likely to
be effective, so owners of bitches who have developed this disease
should be resigned to the fact that spaying is really the safest means
of saving the animal's life.
There is no
evidence to support the notion that bitches who experience oestrous
cycle anomalies or pseudo-pregnancies are more at risk of developing
Pyometra that any other bitch.
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A Clinical Approach To Infertility In The
Bitch
J.L.
Cain and E.C. Feldman
Several unique
features of the canine estrous cycle, together with dog sperm
longevity, allow for dog's high conception rate after a single mating.
Many bitches, however, are seemingly infertile; that is, they fail to
conceive or whelp a normal litter. Determining the cause of apparent
infertility requires a logical diagnostic plan. Because of the
relatively long interval between estrous cycles in the bitch, dog
owners are encouraged to seek veterinary consultation after a bitch's
first reproductive failure. Failure to do so may lead to a false
assessment, misguided treatment, and possible harm to a potential
breeding bitch. The approach to infertility in the bitch described here
is used in the clinical practices of the authors and is presented as a
guide for dog owners and veterinarians to use together.
ESTROUS
CYCLE AND VAGINAL CYTOLOGY:
A brief review
of the canine estrous cycle, including reproductive hormone patterns
and vaginal cytology, follows to provide the necessary background for
understanding the rationale of the diagnostic approach discussed in
this article.
INITIAL
EVALUATION
The initial
evaluation of an apparently infertile bitch includes collecting a
general medical history and complete physical examination. The approach
to infertility outlined here is designed for treating bitches that have
no apparent systemic disease. Also, the current and previous use of any
medication, especially corticosteroids for flea-allergic dermatitis,
must be known in making an accurate evaluation. Routine laboratory
testing (e.g., complete blood count, serum biochemical profile, and
urinalysis) may be indicated on the basis of the animal's history and
physical examination.
The possibility
of Brucella canis infection must be considered in any bitch presented
for infertility, and all dogs should be screened for antibody to B.
canis on a routine basis before breeding.
It is also
prudent to rule out infertility in the male used for breeding before
investigating a bitch for apparent infertility. This is commonly done
on the basis of the male's history (e.g., Was the dog siring litters at
the time the bitch in question was bred?). Semen evaluation may be
necessary to determine the viability of sperm if there is no historical
evidence of male fertility.
CLASSIFICATION
OF INFERTILITY BASED ON ESTROUS CYCLE HISTORY
The apparently
infertile bitch can be classified on the basis of prior oestrous-cycle
characteristics as follows:
normal
oestrous cycle length and normal estrous cycle events
failure to cycle
prolonged interestrous intervals (>10 months);
shortened interestrous intervals (<4 months)
persistent estrus
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1)
Normal Oestrous Cycles:
Bitches with
normal Oestrous cycles are the most common group to present for failure
to conceive or whelp a litter. The potential differential diagnosis can
be investigated by answering the following questions.
Does normal mating occur?
If a bitch will not accept the male for breeding, it is important
to determine if the bitch is in estrus. common management practices may
dictate that bitches be bred on predetermined days of the cycle such as
days 11 and 13 (the first day of proestrus is considered day 1). A
bitch may not be in estrus on these days, however, if her proestrus or
oestrus deviates from the average duration. The use of daily vaginal
cytology and observations of the bitch's behavior in the presence of a
male dog (a teaser) are the most accurate means for determining the
onset of behavioral oestrus.
If the bitch
appears to be in oestrus but refuses breeding, it is possible that a
vaginal or vulvar anatomical obstruction prevents intromission or
causes painful breeding. Careful digital vaginal palpation and
vaginoscopic examination by the veterinarian are indicated. Contrast
radiographic procedures may be necessary to outline anatomical
abnormalities, including vaginal masses; and surgery may be necessary
for resolution of the problem.
Other possible
causes of a bitch's refusal to be bred include the use of an
inexperienced male, behavioral problems (of the bitch or the male), and
mate preferences. the female should be taken to the male's environment
so that he can dominate the breeding event. some bitches that are
transported early in estrus, however, may abruptly terminate estrus
behavior as a result of stress or tranquilization. in such cases,
transportation in advance of an expected proestrus, or the use of
transported semen, may be necessary.
Does mating occur during the bitch's
fertile period?
The bitch may display estrus behavior for longer than the duration of
the time in which she is capable of conceiving. the fertile period can
be estimated retrospectively from vaginal cytology by counting back
five to six days from the onset of cytologic diestrus. again, a bitch
that is routinely bred on predetermined breeding dates may be bred at a
time she is not fertile. this problem most commonly occurs in bitches
that are bred early in estrus. because dog sperm is viable in the
female genital tract for four to 11 days, however, conception can occur
even if the bitch is bred at a non-fertile time. to optimize the
possibility of conception in bitches that have failed to conceive in
the past, we recommend a management program as follows:
the owner should
obtain daily swabs for vaginal cytology beginning on day 1 of proestrus
and continuing throughout estrus.
to
determine accurately the onset of oestrus, the bitch should be "teased"
with a male dog every one to two days beginning when the vaginal
cytology shows signs of late proestrus/early oestrus.
once in
oestrus, the bitch should be bred every two to four days throughout the
duration of oestrus regardless of the number of matings that occur.
the owner should
observe the breedings to be able to report whether they were normal
(ie: whether there was a normal "tie").
pregnancy
should be assessed by ultrasonography 16 to 21 days after breeding.
The
vaginal cytology obtained by this protocol will allow the veterinarian
to:
determine when
the bitch is likely to be in estrus which should be substantiated by
response to the teaser male
determine
retrospectively on the basis of the first day of diestrus, the likely
fertile period of the bitch. if the bitch was bred during this fertile
period, is not pregnant, and the male has been shown to be fertile,
then the bitch should be further investigated for infertility.
Does the bitch ovulate?
A bitch that is determined not to be pregnant by ultrasonography 21 to
28 days after oestrus should be evaluated to determine if ovulation
occurred. Serum progesterone concentration at that time in the cycle
should be in excess of 5 ng/ml. concentrations between 2 and 5 ng/ml
may indicate the bitch has ovulated but is unable to maintain a corpus
luteum (hypoluteoidism, to be discussed later). If the progesterone
concentration is <2 ng/ ml, it is likely the bitch did not ovulate
and should be observed for the occurrence of a "split heat." Split heat
is defined clinically as the situation of a bitch that goes into
estrus, does not ovulate, and is again in estrus within two to four
weeks; it is most common in pubertal bitches. Often, ovulation will
occur after the second estrus. Ovarian cysts can cause ovulation
failure and may be detected by ultrasonography. If ovulation failure
without apparent cause has been documented, the bitch may be induced to
ovulate at the next cycle by injections of human chorionic
gonadotropin. Signs of false pregnancy (a response to a decrease in
progesterone levels) at the end of diestrus can serve as an indirect
and inexpensive indication that ovulation did occur.
Does the bitch have a normal uterus?
When it appears that the bitch's ovarian function is normal (i.e., she
has normal estrous cycles and ovulates), it must be determined whether
the uterus is capable of maintaining pregnancy. Ultrasonography is a
non-invasive method that can be used to evaluate the uterus. In the
healthy non-pregnant bitch, during any phase of the oestrous cycle
other than estrus the uterus is sonographically small and free of
luminal fluid and is commonly not detected at all. An enlarged or
fluid-filled uterus may be an indication of chronic pyometritis or
cystic endometrial hyperplasia. Pyometra can be medically managed with
prostaglandin therapy. Cystic endometrial hyperplasia is most common in
older bitches or in those previously treated with progestational
agents, is diagnosed by uterine biopsy obtained at abdominal surgery,
and is not reversible.
Vaginal cultures
are often obtained in an effort to determine whether a bacterial
infection may be the cause of infertility. The theory behind this
practice is that bacteria present in the cranial vagina may indicate
bacteria in the normally sterile uterus; the problem with this
hypothesis, however, is that bacteria of many types have been isolated
from the cranial vagina, and hence it cannot be considered a normally
sterile environment. A positive culture from the cranial vagina does
not necessarily reflect the presence of bacteria in the uterus. the
only way to determine accurately whether there are bacteria within the
uterus is by uterine biopsy and culture of uterine tissue. bacterial
cultures of the caudal vagina are commonly positive and are indicative
of the normal bacteria that inhabit that area. Overall, vaginal
cultures are of little use in the infertility evaluation unless
vaginitis is present. vaginitis is treated by antiseptic douching.
Does the bitch resorb or abort fetus'?
A bitch that become pregnant then loses the litter before day 30 of
gestation will most likely resorb the fetus', whereas if the litter is
lost later in gestation, the fetus' will likely be aborted. Potential
causes of such a problem include fetal development abnormalities,
uterine or systemic disease of the bitch (including b. canis or canine
herpes virus infection), drug administration and hypoluteoidism.
Resorption or abortion may be suspected in the bitch that is diagnosed
pregnant by abdominal palpation (at approximately day 28 of gestation),
and does not whelp a litter. to determine accurately that a bitch is
pregnant early in gestation, ultrasonography should be performed after
day 16 to 21 of gestation. Routine abdominal radiography can be used to
diagnose pregnancy only after fetal bone calcification-after
approximately day 44 of gestation. when a resorption problem is
suspected, the bitch should be sequentially monitored by
ultrasonography during the next pregnancy and should have a concurrent
serum progesterone analysis to determine if hypoluteoidism occurs. If
the progesterone concentration falls below 2 ng/ ml, the bitch will
likely resorb or abort the fetus', depending on the stage of gestation;
therapy in such cases involves supplementation with progesterone until
day 50. Inappropriately treating a bitch that does not require such
therapy, however, can lead to abnormal development of the fetus' (e.g.,
masculinization of the females) and potential problems with parturition.
2)
Failure to Cycle:
Potential
differential diagnoses for a bitch that apparently fails to cycle may
be investigated by answering the following questions.
Has the bitch ever had an oestrous cycle?
The age of the bitch that has never displayed signs of an oestrous
cycle (primary anestrus) must first be determined. A bitch is not
routinely evaluated for primary anestrus until she is beyond two to
three years of age, although bitches of many breeds (especially of
smaller stature) normally experience a first oestrus (pubertal oestrus)
at a younger age. A bitch with primary anestrus should be evaluated for
signs of an intersex condition. The female genitalia may appear normal,
but the bitch may have abnormal internal reproductive organs and hence
will not cycle. Chromosome analysis may be performed with a blood
sample.
Bitches may have
a silent heat, i.e., they may ovulate but show minimal to no signs of
proestrus or oestrus. This can be determined by monthly evaluation of
serum progesterone concentration to determine whether the bitch
recently ovulated. Weekly determination of vaginal cytology may alert
the owner to the onset of the next proestrus and estrus even though
signs may not be observed, such bitches may be fertile but require
artificial insemination. Future cycles may be associated with normal
clinical signs.
Has the bitch had estrous cycles in the
past and now fails to cycle?
This problem can occur in a bitch that has concurrent systemic disease,
such as an endocrine disorder, a generalized infectious process, or
cancer. Common endocrine diseases include hypothyroidism and
hyperadrenocorticism (cushing's disease). Laboratory tests are
necessary to diagnose definitively such disorders, and with proper
treatment the bitch may become fertile. Another consideration is that
the use of some medications may suppress the hormonal events necessary
for ovarian function. Corticosteroids, frequently administered in the
treatment of skin allergies, may be the cause of secondary anestrus.
The functional
longevity of the ovaries in the bitch is unknown. although ovarian
function generally declines after the bitch is eight to 10 years old,
the ovaries may cease to function earlier (premature ovarian failure).
Pituitary hormone serum concentrations reflect ovarian function because
when the ovaries fail, the pituitary gonadotropins (follicle
stimulating hormone [fsh] and lh) continue to be produced and reach
high serum concentrations. Currently, few centers in the united states
have the facilities for determining fsh and lh concentrations.
Premature ovarian failure is not a treatable condition. This diagnostic
approach also can be used to determine if a bitch with an unknown past
history has been ovariohysterectomized.
3)
Prolonged Interestrous Intervals :
Interestrous
intervals greater than 10 months are considered prolonged in dogs, with
the exception of the Basenji. In aging females (those older than eight
years) the interestrous interval may lengthen. If such prolonged cycles
are fertile, an investigation into the cause of the long interval is
not indicated. Possible differential diagnoses for infertile cycles
that have a prolonged interestrous interval may be explored by
answering the following questions.
Does the bitch have undetected cycles?
A bitch that has a prolonged interestrous interval should be
evaluated to determine if a silent heat is occurring between observed
estrus periods. This may be determined as discussed above. housing the
bitch with another female may induce an earlier cycle.
Does the bitch have an underlying disease
process?
The bitch should be evaluated for underlying disease that can delay the
onset of an estrous cycle. hypothyroidism, in addition to causing
persistent anestrus, can cause a prolonged interestrous interval.
diagnostic testing, including a response of thyroid hormone (t4)
concentration to an injection of exogenous thyrotropin (tsh), is
indicated. when hypothyroidism is the cause of the prolonged
interestrous intervals, other concurrent signs of hypothyroidism,
including dermatologic abnormalities, inappetence, and lack of energy,
are usually apparent.
In bitches with
persistent anestrus or prolonged interestrous intervals, an attempt can
be made to induce estrus hormonally. At the university of California -
Davis, studies are currently under way to evaluate the administration
of gonadotropin-releasing hormone (gnrh) to induce oestrus and
ovulation in bitches. Endogenous gnrh is released from the hypothalamus
and causes the pituitary to release fsh and lh. Administering gnrh
therefore simulates normal physiologic events of the estrous cycle.
4)
Shortened Interestrous Interval:
Cycles that
recur every four months or more frequently are considered abnormal.
Possible
differential diagnoses for this problem can be investigated by
answering the following questions.
Does the bitch ovulate?
Determining the serum progesterone concentration will indicate whether
frequent oestrus periods are associated with ovulations. If they are
not, the bitch may be having a split heat. When she does ovulate, she
should be fertile. Split heat is most frequently associated with young
or pubertal bitches; it is therefore advisable to wait until the bitch
is two to three years old before intervening.
Does the uterus have time to involute?
In bitches that cycle every four months or less and ovulate, the uterus
may not have time to recover from the previous cycle. A uterine
environment that cannot support a pregnancy may develop. In such cases,
one approach to management is to suppress estrus with mibolerone
(cheque drops - Upjohn), an androgenic compound, administered orally
for six months. Suppression of estrus will allow the uterus to involute
completely. The bitch should be bred when estrus recurs after
withdrawal of the drug.
5)
Prolonged / Persistant Oestrus:
Oestrus is
considered prolonged in a bitch that has behavioral signs of oestrus
for longer than 21 days. Possible causes include an estrogen-secreting
ovarian tumor or cyst. Abdominal ultrasonography can be used to observe
ovarian structures. A negative scan does not rule out such a problem,
however, and exploratory surgery may be necessary to visualize the
ovaries. Another possible explanation in cases of apparently prolonged
estrus is that the bitch may have vaginitis, in which case she may
attract males, and this may be mistaken for a sign of oestrus.
Vaginitis can be differentiated from oestrus by vaginal cytology.
reprinted with
kind permission from Judy Bohnert
