What is infertility?
Infertility in a male dog is defined as the inability to produce a successful pregnancy in a fertile female, even with multiple breedings near the time of ovulation.
What are the causes of infertility in female dogs?
Fertility problems in female dogs can be broken down into broad categories: abnormal estrous cycling, failure to copulate (breed), failure to conceive, and pregnancy loss.
Abnormal estrous cycling is a term used to describe a female dog that is not experiencing normal heat cycles. These abnormalities may include delayed, absent, or irregular cycles. A normal female dog should begin having estrous (heat) cycles by two years of age.
There are several stages in the estrous cycle; the stage called estrus refers to when the female is in heat or is sexually receptive. Once these cycles begin, the dog should experience estrus at regular intervals. Most female dogs cycle every four to ten months, although some dogs may only cycle once per year.
Primary persistent anestrus describes a female dog that has reached two years of age without estrous cycling. This condition may be caused by several factors including malnutrition, excessive physical activity, medications that interfere with fertility, or a lack of exposure to other cycling females.
If a dog has experienced one cycle but does not cycle again, secondary persistent anestrus may be diagnosed. This term describes a delay of over 18 months since the last estrus. In some dogs, this is an age-related condition; dogs under two years of age may experience irregular cycles and the same is typically seen in older dogs.
A variety of infections (e.g., E. coli, brucellosis, ureaplasmosis) and metabolic diseases (e.g., renal failure, hypothyroidism, Cushing’s disease) may cause systemic diseases that can lead to a failure to cycle. Exposure to oral and topical steroids (such as those used by humans), hormonal imbalances, and ovarian tumors may also lead to persistent anestrus.
A dog that remains in heat for over six weeks is diagnosed with persistent estrus. Causes of persistent estrus include exposure to exogenous hormones (intentionally or unintentionally), hormonally active ovarian cysts, and ovarian tumors.
Irregular estrus cycling indicates that the ovaries are not functioning properly. In this case, abnormal hormone levels are often responsible for a failure to trigger regular estrous cycles.
Additionally, hormonal imbalances and genetic disorders may prevent normal estrous cycles. Some dogs experience a condition called silent heat, in which they do ovulate but the characteristic signs of being in heat, such as vulvar swelling and discharge, are not observed. Although rare, some dogs may also have an autoimmune disease that affects their ovaries and interferes with estrous cycling.
If the time of fertility is inaccurately estimated, this may lead to the female being unwilling to copulate. Many cases of female infertility are likely related to poorly timed breeding.
Behavioral factors may contribute to a refusal to copulate. These factors include a dominant female dog refusing to stand for a submissive male, attempts to breed a female that is sexually immature, a stressful or otherwise unpleasant breeding environment, and inappropriate behaviors by either the male or female.
Physical factors may contribute to a failure to copulate if they are a source of pain for the female. Common physical factors include hereditary abnormalities of the vagina, a history of vaginal trauma, or vaginal growths. Additionally, conditions such as osteoarthritis or back pain may make females resistant to standing for a male.
What causes infertility in male dogs?
There are many possible causes of infertility in male dogs that can be broken down into three broad categories: failure to copulate (breed) or ejaculate, poor semen quality, and prostatic disease diseases
CAN A DOG BE STERILE? ALL DOGS AREN’T BREEDABLE.
A complete breeding soundness evaluation is essential for assessment of the infertile male dog. Cryptorchidism, a sex-limited autosomal recessive trait, is more common as a unilateral condition. Azoospermia is an ejaculate consisting of seminal plasma but lacking sperm; repeated semen collections in the presence of an estrual bitch will rule out inadequate experience and lack of sexual stimulation. Both carnitine and alkaline phosphatase (AP) are produced in the epididymis; seminal plasma AP concentrations>5000 U/L indicate a normal ejaculate, whereas <5000 U/L is associated with incomplete ejaculation. Benign prostatic hypertrophy (BPH), the most common age-related condition in intact male dogs, is characterized by a sanguineous urethral discharge, hematuria, or hemospermia; diagnosis is based on prostatic enlargement and confirmed by a transabdominal biopsy. Although castration is recommended, valuable breeding dogs can be given finasteride. Prostatitis is more common in older dogs with BPH. Culture of the third fraction of the ejaculate or urine obtained by cystocentesis is indicated. Bacterial prostatitis is treated with antibiotics with high lipid solubility. Some dogs with bacterial prostatitis may develop prostatic abscesses (a medical and surgical emergency). Prostatic cysts are often asymptomatic. Approximately, 5-7% of dogs with prostatic disease have prostatic neoplasia, most commonly adenocarcinoma (it occurs in both intact and castrated dogs), which often metastasizes and has a very poor prognosis. Although a specific diagnosis can be made in many cases of male dog infertility, not all causes are amenable to treatment.