INFERTILITY MANAGEMENT IN FEMALE DOGS
K.P. Singh1 and Praneeta Singh2
Veterinary Officer, Government Veterinary Hospital, Deoranian, Bareilly, Uttar Pradesh Email: drkpsvet@rediffmail.com
2: Assistant Professor, Department of Livestock Products Technology, C.V.A.Sc., GBPUAT, Pantnagar, U.S.Nagar, Uttrakhand Email: vet_praneeta12@rediffmail.com
*Corresponding Author: Veterinary Officer, Government Veterinary Hospital, Deoranian, Bareilly, Uttar Pradesh Email: drkpsvet@rediffmail.com
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:
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Ovarian aplasia: It is the failure of ovary to form properly which is due to a rare congenital problem.
- 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.
