Whenever a breeding does not result in a successful pregnancy, the fertility of both the male and the female should be assessed. It is less challenging to identify causes of infertility in males than it is in females. However, it still can be a difficult process, especially for owners of potentially valuable stud dogs. The owners of the bitch and the male often point fingers at each other, claiming that the other dog is the cause of the problem. This, of course, is not productive. A systematic medical reproductive evaluation of both the male and the female is the best way to determine why a successful pregnancy did not take place. Unfortunately, despite the best intentions of the owners and the veterinary team, sometimes the cause is never determined.
Many breeders bring their male dogs to a reproductive specialist before they are bred, to assess their fertility. The veterinarian will take a thorough history that includes the dog’s familial and personal reproductive history, his past breeding successes or failures (including the method of breeding and type of semen used – fresh, chilled or frozen), his history of illnesses or injuries and his drug and vaccination background, among other things. Diet and dietary supplements should be discussed, as should details of the dog’s living environment such as housing, number of other animals in the household, indoor versus outdoor living, parasite control practices and the like. If the stud dog has been bred but the bitch failed to conceive, her health and reproductive history should also be explored in great detail.
The veterinarian will conduct a thorough physical and reproductive examination. He probably will gently palpate (feel) the testicles and related structures to search for any obvious anatomical defects. The penis and prepuce will be examined for evidence of abnormality or disease, and the prostate will be assessed both by rectal and abdominal palpation. Any reaction of pain during a prostate examination is strong evidence of prostatic disease.
One of the most important parts of a male fertility examination is a semen analysis. The veterinarian will collect a semen sample from the dog manually, and will evaluate it for a number of things, including sperm morphology, motility and concentration. Morphology assesses the percentage of physical abnormalities in the sperm. Motility assesses the percentage of progressively forward-moving sperm (70% is normal in dogs). Concentration is the number of sperm in the ejaculate. This is determined by a mathematical calculation based on the volume of semen ejaculated multiplied by the number of sperm counted per milliliter of semen (200 million is considered normal in dogs).
The veterinarian also will likely submit part of the semen sample - called the spermatic and prostatic fractions – to a diagnostic laboratory for culture, to identify any bacterial or other infections of the testicles or prostate. Semen culture can also identify the presence of mycoplasma, ureaplasma and canine herpesvirus.
The absence of any sperm in a semen sample (called azospermia) may be caused by a testicular tumor, testicular degeneration, testicular underdevelopment (hypoplasia), some physical blockage in the spermatic ducts or retrograde ejaculation. The urethral sphincter muscle in a dog with retrograde ejaculation does not contract (close) normally when the dog ejaculates, causing the semen to be propelled into the urinary bladder rather than out through the urethra. This condition can be diagnosed by evaluating a urine sample taken directly from the bladder (a process called cystocentesis) and looking for the presence of an abundance of sperm.
When sperm are present in a semen sample but only in low numbers (called oligospermia), the veterinarian will look for some abnormality or blockage in the testicles and/or epididymis by physical palpation and use of ultrasound. The testicles are the male reproductive organs that make and secrete testosterone and are the site of sperm production. The epididymis is a long, coiled, cordlike duct running along the border of each testicle, where the sperm mature and are stored.
Other common initial diagnostic tests are routine blood work (a complete blood count and serum biochemistry profile) and a urinalysis. The results of those tests will help to identify the overall health of the dog’s organ systems and can help to identify the presence of infections that may be contributing to infertility. Unfortunately, sometimes the initial data base results are unremarkable. Other blood tests are available to measure the levels of circulating sex and thyroid hormones, including testosterone and estrogen, which may or may not be diagnostically helpful.
Males suspected of infertility should be tested for brucellosis by a simple blood test, especially if they were not tested for this infection before all prior breedings and even more so if all females that they bred were not tested. Brucellosis is a serious, highly contagious sexually and orally transmitted disease. The infectious microorganism, Brucella canis, is shed in large numbers in the semen, vaginal secretions and urine of infected dogs.
Other diagnostic tools are abdominal radiographs (X-rays) and ultrasound to assess the integrity of internal reproductive organs. Radiographs can be particularly helpful to identify infections, tumors or other abnormalities of the urinary tract, prostate and testicles. Radiographs can also detect a fractured os penis, which is the bone that is part of the penis in male dogs. A biopsy and assessment of testicular tissue can provide a great deal of information about low sperm levels and the likelihood that the dog may respond to medical therapies. Biopsy samples will be submitted to a diagnostic laboratory for complete analysis.
Finally, a process called karyotyping, which involves analyzing the exact number, shape and size of each paired chromosome, can be used to diagnose genetic and chromosomal defects that cause intersex abnormalities.
Because the causes of infertility in male dogs are so variable, diagnosing the precise cause of the problem can be difficult. However, in most cases the reason for his infertility will usually be determined.