Infertility and Breeding Disorders

Chapter 94 Infertility and Breeding Disorders



Robert V. Hutchison



FEMALE DOG


Realizing the uniqueness of the reproductive system is essential when dealing with canine infertility. Unlike other domestic species, the bitch ovulates into a progesterone environment rather than estrogen. At the time of ovulation, the canine ova are a primary oocyte. Before fertilization can occur, the ova must under go a second mitotic division and shed the associated polar body. Specific knowledge of the reproductive physiology is essential to achieve successful conception and pregnancy.



Normal Estrous Cycle


The normal estrous cycle occurs approximately every 6 months but may vary between 4 and 18 months based on the individual, breed, and family history. The normal estrous cycle of the bitch consists of four distinct phases.



Anestrus



• The time period between estrous cycles.

• Anestrus is associated with a serum progesterone level of less than 2 ng/dl with no vaginal swelling or discharge.

• Follicle-stimulating hormone (FSH) levels are elevated throughout the anestrus period.

• The anestrus period ranges between 4 and 18 months in duration. Dogs require a minimum period of 4 months to permit the uterus adequate time to repair and regenerate, permitting normal implantation on subsequent breedings.


Proestrus



• The period of bloody vaginal discharge, pheromone changes, and rising estrogen levels. This phase lasts between 3 and 14 days.

• The rising estrogen levels thicken the vaginal walls, causing the changes in epithelial cells detected on vaginal smears.

• The concentration of serum progesterone during proestrus is less than 2 ng/dl.

• Cells lining the ovarian follicles begin producing progesterone levels in the 2- to 3-ng/dl range, triggering the release of LH from the pituitary and inducing ovulation within 48 hours.

• The bitch normally begins flagging and standing at the time of the LH release.

• Swelling of the vulva is observed. Although males are attracted to the bitch, they are not permitted to breed.


Estrus



• The period of ovulation, male acceptance, and conception.

• Ovulation occurs when the serum progesterone is between 4 and 10 ng/dl.

• Estrus lasts until approximately 6 days after ovulation.

• The progesterone continues to rise steadily, reaching ranges of 15 to 50 ng/dl within 72 hours post-ovulation, and continues to be elevated during the diestrus period.

• At this time, the female “flags” her tail and is willing to stand for the male to mount and breed.

• The vulva is soft, and a blood-tinged to clear or straw-colored discharge may be evident.

• It is not uncommon for the discharge to remain slightly bloody.


Diestrus



• Begins 6 days post-ovulation and is the end of the fertile period.

• Diestral progesterone levels are not affected by pregnancy.

• Diestrus lasts until the serum progesterone levels drop below 2 ng/dl. Diestrus lasts approximately 8 weeks in the pregnant bitch and can last 2 to 4 months in non-pregnant bitches.

• The first day of diestrus is characterized by a dramatic change seen on a vaginal smear. The superficial cells seen in estrus are replaced by parabasalar and intermediate cells. WBCs also begin to appear on vaginal cytology as the bitch moves from estrus to diestrus.

• A slight mucoid vaginal discharge may be apparent.


Etiology of Conception Failure



Poor Semen Quality


Few studies have been done to determine the minimum number of normal spermatozoa necessary for conception to occur. Numbers previously thought to be required were in the 100 × 106 to 150 × 106 range. There have been successful conception and whelping from bitches inseminated with less than 30 × 106 normal spermatozoa.


See later in this chapter under “Male Dog” for more information on semen evaluation.



Ovulation Failure



• The fact that a bitch shows the physiologic signs of an estrous cycle does not guarantee that the cycle will be ovulatory.

• The only laboratory method to confirm ovulation is an increase in serum progesterone level to greater than 4 ng/dl.

• Split and non-ovulatory cycles are not uncommon in the bitch. A progesterone rise to 2 to 3 ng/dl does not guarantee that ovulation will occur.


Improper Timing of Breeding



• Historically, veterinarians and breeders have timed bitches using vaginal smears, breeding guns, and physiologic signs such as color of vaginal discharge, days of the cycle, and vulvar softness. These traditional methods of breeding timing were not only flawed but also, in many cases, irrelevant to ovulation timing.

• The average length of an estrous cycle varies from 17 to 28 days. Extremes in ovulation varying from 6 to 32 days after onset of the estrous cycle with successful breeding having been confirmed.

• Fresh semen lasts an average of 4 to 6 days in the oviducts.


Methods of Timing of Ovulation



• Serum concentration of estrogen (which is not a precise method of timing)

• Luteinizing hormone assay

• Serum concentration of progesterone—more reliable in pinpointing ovulation


Luteinizing Hormone Assay


• The release of luteinizing hormone (LH) by the pituitary triggers ovulation within 48 hours. Perform LH testing and use serum progesterone to confirm that the ovary has responded to LH release and that ovulation has indeed occurred.

• Current LH testing consists of a wicking test (Status-LH, Synbiotics, San Diego, California). The test requires 4 drops of serum. A red line occurs when the LH rises above 1 ng/dl.

• Because of the short duration of LH (12–24 hours) in the bitch’s circulation, perform the test daily.

• LH in the canine is species specific and assays with non-canine reagents cannot be used.


Progesterone Assay


• LH release, the initial rise in progesterone to 2 to 3 ng/dl, followed by ovulation 48 hours later has made timing the bitch an available and easily performed procedure.

• The bitch ovulates a primary oocyte, requiring 48 hours post-ovulation for ova maturation. After the ova have reached the secondary oocyte stage, it is thought that the eggs are fertilizable for up to 36 hours.

• The timing of a breeding is based on anticipated semen survival time.

• A serum progesterone level of 5 ng/dl indicates that ovulation has occurred.

• Canine progesterone is not species specific and can be tested for using a number of testing methods. Enzyme-linked immunosorbent assay (ELISA), chemiluminescence, 3-Immulite, and radioimmune assay (RIA) using conjugated and non-conjugated serum are all testing methods available to the practitioner. The preciseness needed, the type semen most frequently used, and the frequency of result reporting will dictate which method best fits a practice’s needs.



Key Point


Frozen canine semen lasts in the bitch 12 to 24 hours. It is important that frozen semen not be inseminated until ova have reached the secondary oocyte stage due to the frozen semen’s short life span.



Improper Breeding Methods


The canine breeding system is one that involves intromission into the vaginal tract of a semi-flaccid penis containing an os penis then engorgement of the penis and bulbus glandis. Ejaculation enters the vaginal tract at the external os of the cervix. The engorged bulbus glandis causes the “tie” that stimulates hormonal release, causing the semen to be “pumped” through the cervix and into the uterus. The spermatozoa then move cranially up the uterus and enter the oviducts, where conception occurs.


• The cervix in the bitch is located within the abdominal cavity, dorsal to the bladder.

• The length or distance from the vulva to the external os varies by breed size.

• It is essential that the semen be deposited at the external os of the cervix.

• Natural breeding resulting in outside ties or incomplete penetration into the bitch and poorly positioned rods for vaginal artificial insemination significantly decrease conception rates.



Key Point


Artificial insemination methods such as transcervical insemination (TCI) and surgical or laparoscopic intrauterine deposition of semen permit breeding that bypasses the vaginal cavity and cervix. These methods of depositing the semen into the uterus have contributed greatly to the current success of canine frozen semen.



Implantation Failure


After spending 6 to 10 days in the oviducts, the fertilized ova are released into the uterus. Implantation occurs in the bitch 17 to 18 days post-ovulation. Inflammation of the endometrium, cystic endometrial hyperplasia (CEH), and uterine fibrosis can contribute to implantation failure.



Refusal to Accept the Male


Refusal of the bitch to accept the male can be a significant problem in breeding. Use the following methods to address this problem:


• Confirm the anticipated ovulation timing. Vaginal cytology will confirm if ovulation has previously occurred.

• Change the environment (indoors versus outdoors, male’s home versus female’s home, etc.).

• If necessary, it is better to perform an artificial insemination than to risk injury to canine or human components.


Inability to Achieve a “Tie”



• Examine the vulva, vestibule, and vagina of the female for strictures, bands, size, etc.

• Check the male for penile abnormalities such as a persistent penile frenulum or adhesions to the prepuce (see Chapter 88).

• Check the prepuce and fornix for mass lesions, ulceration, or foreign bodies (see Chapter 88).

• Evaluate both the male and the female for non-reproductive health issues.


Resorption and Abortion



• Total resorption of fetuses can occur up to 38 days after ovulation. Numerous conditions can cause fetal death, including genetic or chromosomal anomalies, hormonal imbalance, chemicals and drugs, infectious agents, and toxins.

• Pedigree analysis, histopathology of the aborted placenta and fetuses, uterine biopsy, and microbiologic testing may help determine the cause of the problem. A thorough history of medications and chemical exposure and an evaluation of dietary supplements and ingredients are essential when confronted with resorption or abortion of fetuses.

• Consult the recommendations of the manufacturer before any drug is given to a pregnant bitch (Table 94-1).


Table 94-1 COMMON DRUGS TO AVOID DURING PREGNANCY


Antifungals


Tetracyclines


Estrogens


Testosterones


Corticosteroids


Nonsteroidal anti-inflammatory drugs



Diseases of the Breeding Bitch



Failure to Have an Estrus Cycle



• Normal females can be up to 24 months of age before having a first estrous cycle.

• Bitches over 24 months with no clinical or physiologic signs of an estrus cycle should initially be tested for thyroid and cortisol abnormalities.

• A serum progesterone level of <2 ng/dl will rule out any missed or silent season during the previous 2 months.

• If normal hormonally, a karyotypic examination should be performed. Karyotyping is performed on a heparinized blood sample by specialty labs.

• The normal karyotype of the canine consists of 78 chromosomes (78 XX for the bitch and 78 XY for the male).

• If no hormonal or chromosomal abnormalities are detected, consider endoscopic or surgical evaluation of the ovaries (see Chapter 91).


Prolonged Anestrus after an Estrous Cycle



• Normally, anestrus can vary from 4 to 12 months. Bitches in anestrus longer than 12 months should be examined for hormonal anomalies, including thyroid, cortisol (either elevated or decreased), and progesterone levels.

• Perform an ultrasound examination of the ovaries for cystic structures.

• Endoscopic examination or exploratory surgery may be necessary to rule out fibrotic or hypoplastic ovaries, an unknown ovariohysterectomy, or ovarian cysts (see Chapter 91).

• The fluid aspirated from the ovarian cyst should be evaluated for progesterone. Many of these cystic fluids will contain progesterone levels >50 ng/dl acting to suppress the estrous cycle.


Split Estrus Cycle



• A split cycle is characterized by the bitch entering proestrus but never ovulating.

• The bitch normally will recycle in 4 to 6 weeks, the “second” cycle usually being ovulatory and breedable.

• Split cycles are diagnosed more commonly because of the routine use of progesterone testing for breeding management.


Silent Seasons



• Silent seasons are characterized by a bitch ovulating but showing no external signs of an estrous cycle.

• A silent season is usually first suspected when a bitch, having had no observable estrous cycle, has a pseudocyesis or “false pregnancy.” Pseudocyesis confirms that ovulation has occurred within the last 8 to 10 weeks.

• To determine when the estral phase of a silent season occurs, perform a weekly vaginal smear, observing the cellular changes from parabasalar and intermediate vaginal epithelial cells to superficial epithelial cells.
• The cellular changes indicate a rise in estrogen. Once the rise in estrogen is confirmed, serum progesterone levels are performed to determine the day of ovulation.


Shortened Anestrus



• Due to the inflammatory effect of progesterone on the endometrium, a minimum of 135 days (4 months) is needed for endometrial repair following an ovulatory season.

• Bitches cycling at intervals of less than 135 days may have reduced fertility due to the lack of endometrial integrity.

• This symptom is most frequently seen in German shepherds, Newfoundlands, rottweilers, and Welsh corgis.

• Mibolerone, an androgenic medication, can be given daily to delay the onset of the estrous cycle and to allow endometrial healing.


Prolonged Estrus



• Prolonged bleeding can be commonly seen in young bitches having their first estrous cycle.

• Bitches may have multiple non-ovulatory cycles. Serum progesterone concentrations from these bitches remain below 2 ng/dl.

• In young bitches, no treatment is usually necessary, and bitches will begin normal interestrous intervals after they have had an ovulatory cycle. This is not an indication of cystic ovaries.

• A prolonged estrous cycle in older bitches is of much more concern. Estrogen-secreting ovarian cysts and tumors are prime etiologies.

• Vaginal cytology showing predominately superficial cells will confirm estrogen as the cause of the vaginal bleeding.

• Examine bitches with prolonged vaginal bleeding not caused by elevated estrogen for other causes, such as bleeding disorders, vaginal disease and neoplasia, as well as hemorrhagic bladder disease.


Puppy Vaginitis



• Puppy vaginitis is the term used to describe the vaginal mucus in puppy bitches yet to have their first cycles (also see Chapter 92).

• Puppy vaginitis is a physiologic syndrome that does not require treatment. The condition is self-correcting when the estrogen surges during the bitch’s first estrous cycle.


Vaginal Discharge



• Evaluate all vaginal discharges microscopically. Characterize the discharge as hormonal versus non-hormonal, inflammatory versus non-inflammatory, and infectious versus non-infectious (see Chapter 92).

• Etiologies of vaginal discharge include vaginitis, pseudocyesis, pyometritis, cystitis, estrous cycle, pre-whelping, post-whelping, mibolerone therapy, and vaginal tumors.



Key Point


If vaginal discharge is determined to be infectious, perform cultures for aerobes, anaerobes, and mycoplasma or ureaplasma.

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Infertility and Breeding Disorders

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