INFERTILITY IN DOGS
K.P.Singh1, Bhoopendra Singh2 and Praneeta Singh3
Veterinary Officer,
Government Veterinary Hospital, Deoranian, Bareilly, Uttar Pradesh
2: Assistant Professor, Deparment of Animal Reproduction, Gynaecology and Obstetrics, C.VSc.& A.H., NDUAT, Kumarganj, Faizabad, Uttar Pradesh
3:Assistant Professor, Department of Livestock Product Technology, C.V.A.Sc., GBPUAT, Pantnagar, U.S.Nagar, Uttrakhand E mail: vet_praneeta12@rediffmail.com
Infertility is defined as incapacity to procreate (reproduce). When dealing with infertility, both the dog and the bitch must be considered. Ninety percent of infertility is due to poor breeding management such as breeding at the wrong time or not breeding often enough and the male could have poor sperm quality. Acquired infertility is very common in the dog. If more than a couple of months have passed since the dog’s last litter, it may now be infertile. Illness before, during or after breeding could explain why the bitch did not conceive, likewise, a fever or other illness can adversely affect semen production and it takes about 60 days for the sperm cells to regenerate after such an insult.
Breeding soundness examination of male dogs:
A breeding soundness examination can be conducted to evaluate the male dog. It typically includes a general physical examination and an examination of the external genitalia. Abnormalities such as severe arthritis or spinal problems may not allow a dog to mount. Hormonal diseases such as Cushing’s disease can also reduce fertility. The penis and prepuce should be examined for abnormalities, such as a persistent frenulum, growths or inflammation of the prepuce (posthitis),that may prevent normal intromission. The ospenis should be palpated for fractures. Abrasions or lacerations on the penis may bleed during coitus causing blood to be in the semen. The prostate should be palpated via the rectum. Inflammation of the prostate (prostatitis) may be painful and can prevent the dog from finishing mating or make him appear to have a lowered libido. White blood cells (WBCs), red blood cells and bacteria from the prostate may damage sperm viability. Also, an infection in the prostate can potentially ascend to cause an infection in the testicles (orchitis). The scrotum, testicles, and epididymides are also palpated. The size of the testicles correlates with the amount of sperm seen on collection of an ejaculate. Small and soft testicles are often associated with poor semen quality. Greatly enlarged testicles suggest an infection and lumps in the testicles are suggestive of tumours. Scrota abnormalities such as dermatitis, may adversely affect sperm quality.
An ejaculate of semen should be collected and evaluated for colour, volume, total and progressive motility, concentration, shape (morphology) and the total number of normal sperms should be calculated. There are three distinct outcomes of a breeding soundness examination: (1) normal sperm parameters, (2) abnormal sperm parameters and (3) no sperm seen in the ejaculate. Volume varies with the amount of prostatic fluid collected but is generally 2 to 20 ml. Sperm motility should be evaluated immediately and normal dogs should have 75% to 80% progressively motile sperm (i.e. sperm that are moving in a forward direction). A sample of the sperms should be prepared for microscopic evaluation. It is important that the shape of the sperm be evaluated so that the total number of normal shaped progressively motile sperm inseminated is known as only these will fertilize an oocyte or egg.
Sperm concentration (number of sperm/ml) can be determined by using a special sperm cell-counting device (called a densimeter) or other methods. The total number of sperm in the ejaculate is calculated by multiplying the concentration by the volume; normal is about 10 x 101 sperm/lb of body weight. Therefore, a small dog can be expected to produce about 20 x 106 sperm ejaculate and a large dog about 70 x 106. Infertility is very rare in dogs with normal semen parameters. Management problems and bitch infertility should be considered when sperm findings are normal.
If abnormal sperm parameters are found, the dog should be rechecked in 2 to 3 months to see if the problem is transient. The veterinarian should be informed of any recent illness and any medications (especially anabolic steroids) that the dog has received. Although the actual cause for abnormal sperm parameters is often never found. Possible causes, including inflammation of the scrotum, testicular neoplasia, trauma, brucellosis, should always be ruled out. Inflammation of the scrotum can cause a high scrotal temperature that is deleterious to sperm production. An ultrasound of the testicles can be performed to evaluate for testicular neoplasia, as some tumors of the testicle are not palpable. This problem can be treated as unilateral castration of the affected testicle often restores normal sperm parameters. If no inciting cause of the sperm abnormalities can be found, the case becomes very frustrating for both the owner and the veterinarian.
The absence of sperm in the ejaculate (azoospermia) can have three possible causes:
(1) the dog’s testicles are not making sperm, (2) the testicles are making sperm, but the sperm cannot get out because the epididymides are blocked and (3) the testicles are making sperm (which can get out) but a complete ejaculate was not collected. When there are no sperm in the ejaculate, the fluid can be tested for alkaline phosphatase, which is made by the epididymides. A high level of alkaline phosphatase indicates that epididymal fluid was collected. If epididymal fluid was collected and there are no sperm, it is likely that the testicles are not producing sperm. A low level of alkaline phosphatase indicates that the epididymis is blocked or that a complete ejaculate was not obtained. In this case, repeated samples should be collected and an estrous bitch can be used as a teaser to obtain an ejaculate. A careful palpation and ultrasonography of the epididymides should be performed to detect any abnormalities. If the azoospermia persists, a testicular biopsy can determine whether the testicles are producing sperm. However, this procedure is rarely performed. The biopsy procedure itself may severely damage the testis and it does not seem to matter whether the testes are producing no sperm or sperm are being produced but cannot get out neither condition is treatable.
Infertility in female dogs is the inability to produce live offspring. This can be caused by failure to ovulate, cycle normally, accept a male, conceive, maintain the pregnancy or deliver live puppies at full term. Fertility requires a normal heat cycle and ovulation of healthy eggs into a healthy reproductive tract, followed by fertilization of those eggs by healthy sperm. The embryos must successfully implant in the uterine lining, develop into normal foetuses and be delivered alive after the pregnancy is successfully maintained. The most common cause of infertility in female dogs is bad timing. Silent heats, split heats, abnormally long heats, missed heats and irregular heats all can contributes to breeding management’s nightmares and errors. Other causes of infertility are vaginal and uterine infections, hormonal irregularities, stress, poor nutrition, anatomical abnormalities and genetics.
The most important aspect of evaluating infertility in the bitch is the history. The main purpose of the history is to ascertain if there is a problem with cyclicity, management, the stud dog or if the apparent infertility is actually pregnancy loss.
There are basically following types of bitches on the basis of cyclicity.
Bitches with Normal Cycles:
Bitches that cycle normally generally have a 5 to 10 months interestrous interval. A general physical examination of the bitch, an examination of the vulva and a digital examination of the vestibule and caudal vagina should be performed. Vestibular strictures may prevent normal intromission by the penis and cause an outside tie (i.e. when the bulbus glandis engorges before entering the vagina and is thus too large to fit through the vulva) or may cause the bitch so much pain that she will not allow breeding. Vaginal anomalies including a persistent septum (a band of tissue dividing the vagina into two parts), segmental aplasia (a missing portion of the vagina), or a persistent hymen may be present. Such problems can sometimes be surgically corrected. Although not of much importance themselves, the presence of abnormalities in the vulva, vestibule or vagina may suggest irregularities in the remainder of the reproductive tract.
Exploratory abdominal surgery (laparotomy) or contrast radiography may help assess abnormalities in the more cranial portions of the reproductive tract (e.g., cervix, uterus, oviducts and ovaries). Vaginal prolapse may preclude normal penetration by the male. Vaginal hypertrophy (enlargement of the vaginal floor) may occur during estrus and interfere with natural mating. A culture may be taken from the vagina but results are essentially meaningless in the absence of clinical signs of vaginitis (discharge, odor). Aerobic bacteria may be cultured from the vagina of all normal bitches. Mycoplasma is present in 80% of normal and fertile bitches. Any organism cultured in the absence of clinical signs other than Brucella canis is considered a normal inhabitant of the vagina. The only bacterium that would indicate a cause of infertility on vaginal culture is B. Canis. However, B. canis requires special culture conditions. Many stud dog owners require vaginal cultures prior to breeding because they are concerned particularly about Mycoplasma. They hope to prevent infertility in the stud dog by preventing him from mating with an infected bitch. However, Mycoplasma is a normal inhabitant in 70% to 80% of dogs and bitches and treating a perceived “infection” in an infertile dog does not restore fertility.
If the physical examination is normal and a management problem cannot be detected, the veterinarian may wish to follow the bitch through a complete cycle to ensure that she is cycling normally, has a normal rise in progesterone and normal luteal phase (evaluated by testing progesterone levels throughout the 2 months after the heat cycle) and most importantly, was bred at the optimum time. Remember, the potential fertility of a bitch cannot be evaluated unless she is bred to a fertile male. Was the male impregnating other bitches that were bred around the same time as the one that failed to conceive? When was the stud dog’s last litter? Was the stud dog sick in the 2 months prior to breeding this bitch? If a solid history of the male cannot be obtained, a breeding soundness examination should be performed on the bitch. Management problems should be corrected and an optimum breeding management program should be outlined with the help of a veterinarian. As mentioned, the best follow up is to have a veterinarian who is interested in canine reproduction follow the bitch through the next heat cycle. This, along with serial progesterone levels and serial vaginal cytology, will pinpoint the optimum time to breed the bitch.
The quality of the breeding can be important. A natural tie is the best guarantee of a successful insemination. In cases of an outside tie, the tip of the penis can be held tightly by the handler just behind the glans and a fairly normal ejaculation should occur. Conception rates can be normal with outside ties. Artificial insemination is only as good as the person performing it. Although the technique is very simple in dogs, once the sperm is outside the dog, it is exposed to many insults including mishandling, toxins, cold or heat shock and improper insemination techniques. Breeders should determine how experienced the inserninator is and what his or her pregnancy rate is a good inseminator should have a pregnancy rate approaching that of natural breeding. Conception rates with chilled extended semen and frozen semen remain disappointingly low and these are not recommended for bitches with infertility problems. If a bitch was bred with one of these methods and did not conceive, breeding should be tried again using fresh semen before suspecting that she has a fertility problem.
A possible but not well documented cause of conception failure and/or pregnancy loss is subclinical uterine infection. Signs include vulvar discharge during diestrus and apparent embryo loss after a positive ultrasound. Treatment can include prophylactic antibiotics on the next heat cycle. Enrofloxacin is administered from the first day of bleeding until 1 week after the last breeding. Cephalexin is then administered until whelping. These bitches should have ultrasonograms to detect pregnancy 30 days after the last breeding.
Bitches with Abnormal Cycles:
The bitch with abnormal estrous cycles may have persistent anoestrus (lack of cycles), long interestrous intervals or short interestrous intervals.
Persistent anoestrous (lack of cycling)
A bitch is considered as having persistent anoestrous when she fails to cycle by 24 months of age. A bitch that is less than 2 years old and not cycling may not have reached puberty yet. Some large breed bitches do not have their first heat cycle until they are 2.5 years of age or older.
Cause of anoestrous may be due to the following:
a. Previous desexing:
Most puppies are now desexed as early as 7 weeks of age. Some owners may be unaware that his/her purchased bitch has been previously desexed.
b. Silent heat:
This occurs in bitches where the ovary is active but swelling of vulva, vulval bleeding and attraction of male dog are absent. Bitches that are thought to have silent heat can be diagnosed by taking monthly progesterone assays or conducting weekly vaginal smears investigation. If the progesterone level rises above 2 ng/ml or vaginal smears show an increasing number of cornified cells the bitch is diagnosed to have a silent oestrous.
c. Sexual abnormalities:
A dog may appear as a female but has abnormal chromosomes (i.e. genetic materials) or have male gonads but with female external genitals (male pseudohermaphrodite). Such dog can be determined via visual inspection of abnormal external genitals, biopsy of each gonadal tissue, measurement of hormone levels or assessment of karyotype.
d. Drug induced anoestrous:
Bitches receiving androgens (e.g. anabolic steroids) or progesterone may not cycle. In addition, bitches on medications for health or behavioural problems can have interference to their oestrous cycles, whilst bitches receiving corticosteroid (i.e. cortisone) often have reduced fertility.
e. Hypothyroidism:
It is the most common hormonal disorder of dogs and in some cases cause infertility. Noticeable reproductive signs have been reported in some bitches that are hypothyroid. Such signs include anoestrous, prolonged or irregular intervals between oestrous cycles, reduced intensity or duration of oestrous cycles, increased incidents of spontaneous abortion, stillbirths, mummified puppies and small size puppies. Non-reproductive signs also appear in some affected bitches which include lethargy, obesity, hair loss and slow hair regrowth.
A tentative diagnosis of low thyroid hormone can be made based on medical history and clinical signs, but a definitive diagnosis requires a series of thyroid blood tests.
L-thyrosine is required to be administered twice daily by mouth to supplement the low body thyroid level when hypothyroidism level is confirmed. The blood thyroid level is then retested 4 to 6 weeks later to ensure the level has risen satisfactorily and then routinely recheck each 6 months. The bitch should resume normal cycle within 4 to 6 weeks of treatment if the problem of anoestrous is due to low thyroid level.
f. Systemic disease:
Bitches with diseases such as kidney failure or cancer are often less likely to cycle than normal bitches. Full blood and urine tests must be performed in bitches with primary anoestrous to ensure the bitch in question is not affected by systemic disease. Further, dogs that are suffering from Cushing’s disease may have a persistent anoestrous due to elevated blood cortisol level causing reduction in Lutenizing hormone (a reproduction hormone) production and release.
g. Ovarian cycts:
Ovarian luteal cysts may produce progesterone levels above 2 ng/ml, and this in turn can affect the ability of pituitary glands to release adequate level of Gonadal Releasing hormone (a reproductive hormone), which in turn inhibits cycling. Such cysts can be diagnosed by demonstrating persistently elevated progesterone levels.
h. Ovarian aplasia:
It is the failure of ovary to form properly which is due to a rare congenital problem.
i. Immune-mediated oophoritis:
A condition that the body’s immune system self destroys the ovary.
Secondary anoestrous:
This is a failure of the bitch to cycle within 10 to 18 months of the previous cycle. It may due to low blood thyroid level, Cushing’s disease, ovarian cysts that secrete progesterone, or cortisone administration.
Long interestrous intervals (i.e., over 10 months) may be a normal variation, especially in larger and/or older bitches. There is no good way to bring a bitch into a fertile heat cycle, so the breeder will have to wait for her to cycle. Thyroid function can be checked as for the bitch with no cycles.
Short interestrous intervals may lead to infertility because the uterus does not have enough time to return to its normal size and shape (i.e., involute) after whelping or the previous heat cycle. The interestrous interval can be lengthened by treating the bitch with megestrol acetate for 32 days. Treatment should begin a few weeks before she is expected to come into heat. That expected heat cycle will not occur and the bitch should come into a heat 4 to 6 months after the end of megestrol acetate treatment. The bitch can be bred on this cycle and may be fertile if shortened interestrous intervals were her only problem. Because megestrol acetate is a synthetic progestogen, its use may be associated with an increased risk of endometritis and pyometra, as would be seen with any endogenous or exogenous progestogen. However, the percentage of bitches affected is small.
Short interestrous intervals seem to relate to inadequate luteal phase. The progesterone level continues to rise after ovulation but drops to baseline after 1 month to 6 weeks. The normal luteal phase is 60 to 70 days. An inadequate luteal phase is documented by serial progesterone samples every few weeks throughout pregnancy. The progesterone level should remain above 4 to 5 ng/ml for 60 days. If documented luteal insufficiency exists, the bitch can be supplemented with progesterone in oil for 56 to 58 days after ovulation. Progesterone must be discontinued at that time to allow normal whelping.
Split heats occur when a bitch grows follicles on her ovaries and experiences the signs of proestrus (swollen vulva, vulvar bleeding and attractiveness to males) but does not progress into estrus and does not ovulate. The bitch’s follicles will usually regress and then she will come into a complete heat cycle with ovulation anywhere from 2 to 12 weeks later. Split heats are most common in a young bitch, especially at her first season and are not considered to be associated with infertility when bred on the cycle in which ovulation occurs. Split heats must be differentiated from short inter estrus intervals between two true heat cycles. A vaginal smear will show red blood cells and intermediate and superficial cells as would be expected during proestrus but in a split heat will not progress into an estrus smear (anuclear superficial cells). If vaginal smears are collected for a sufficient time, they will change to an anestrous smear characterized by parabasal cells and WBCs. The vaginal smears for true heat cycles with shortened inter estrous intervals will progress normally.
