In the most general sense, infertility in male dogs is defined as the inability to sire a litter. It does not necessarily mean that the dog is sterile.
Causes of Infertility in Male Dogs
Infertility in dogs can be congenital (present at birth) or acquired during their lifetime. In many cases, failure to produce a litter is caused by improper breeding management and timing, rather than true infertility on the part of either the male or the female.
Underdeveloped testicles (testicular hypoplasia)
Undescended or retained testicles (cryptorchidism; if bilateral, the dog will be sterile; if only one retained testicle, the dog may be fertile)
Persistent penile frenulum (a piece of skin remains attached between the prepucial sheath and the penis, preventing normal extrusion of the penis and successful mating)
Phimosis (the prepucial opening is too small for the penis to come out of it and accomplish a breeding)
Chromosomal abnormalities (intersex disorders; these involve the intermingling, to varying degrees, of the characteristics of both sexes in one animal, including anatomical form, reproductive tissue and organs and sexual behavior)
Anatomical abnormalities of the penis
Anatomical abnormalities of the prepuce
Infertility in male dogs can also be acquired after birth, for a number of reasons. These include:
Testicular or scrotal trauma
Testicular or scrotal infection
Testicular inflammation (orchitis)
Testicular torsion (extremely serious; potentially fatal)
Fracture of the bone of the penis (os penis)
Infection or inflammation of the prostate gland (prostatitis)
Trauma to the prostate gland
Inflammation anywhere along the male genital tract (by Brucella canis or other infectious microorganisms)
Immune-mediated diseases or disorders
Metabolic diseases or disorders
Prolonged exposure to certain drugs (steroids; anti-cancer drugs/chemotherapy; estrogen; androgen; progesterone; certain antibiotics; others)
Exposure to environmental and chemical toxins
Prolonged exposure to temperature extremes
Inbreeding (the mating of very closely related dogs; mother to son, father to daughter, etc.)
Excessive sexual activity is a significant cause of temporary infertility in male dogs. Most authorities recommend that a dog bred on 3 consecutive days should be rested for the following 2 days, at a minimum. Some males can be bred every other day and maintain a high sperm count, but they still will require rest periods to prevent impotence (loss of libido or sex drive).
One of the reported hormonal causes of canine infertility is hypothyroidism, which usually is an acquired condition. Low thyroid hormone levels affect both sperm count and sex drive. Diabetes mellitus can also cause infertility by decreasing the sperm count in affected dogs. Hypogonadism is a poorly understood disorder that involves a decrease in one or more sex hormones that cause abnormalities in sperm numbers and motility. Diseases or disorders of the pituitary and adrenal glands are other acquired hormonal causes of infertility in male dogs.
Low testosterone levels can lead to a low sex drive. Testosterone is a hormone that is produced by the testes and is critical to the male libido. Testicular diseases, including cancer and infection, can diminish or destroy a dog's sex drive. Testicular sertoli cells produce estrogen, which acts to neutralize the effects of testosterone. Sertoli cell tumors are uncommon but they do happen in domestic dogs and can contribute to infertility.
In some males, infertility is caused by failure of the internal urethral sphincter to contract (close) when the dog ejaculates. When this happens, semen is ejaculated upstream into the dog's urinary bladder, rather than out the urethra and into the female's vagina. This condition is called "retrograde ejaculation."
Psychological factors can contribute to canine infertility, in both males and females. Some male dogs are scolded and punished by their owners for showing sexual behavior ("humping") and/or aggression towards other dogs or people. This can create an unpleasant association with mating. Some bitches can be extremely aggressive during breeding, which may traumatize participating males and make them fearful of sexual activity. Dogs raised exclusively indoors with people may be reluctant to mate simply because they are uncertain about their rank with other dogs. Physical pain, in the genitalia or in the legs, can also inhibit a male dog's desire to breed.
Prevention of Infertility
It is impossible to make meaningful generalizations about effective ways to prevent infertility in male dogs, because the causes can be so variable. However, exposure to temperature extremes – hot or cold – should be avoided. Care should be taken in selecting appropriate bedding materials and when bathing male dogs, so that their genital areas are not irritated or traumatized. Male dogs should not be bred daily for any prolonged period of time, and inbreeding should be avoided by all but the most seasoned of breeders. Breeding animals should be kept away from environmental and household toxins and should not be given drugs for longer than medically necessary. Perhaps most importantly, infertility can be prevented by sound, thoughtful, well-managed breeding programs and practices on the part of both the stud and the bitch owners.
The most common cause of infertility ("failure to produce puppies") is poor or inadequate breeding management practices – especially improper timing and coordination of matings. It takes about 60 days for sperm to mature within the canine reproductive tract. As a result, infertility caused by testicular problems will take roughly 2 months to resolve, if resolution is possible.
Symptoms of Infertility in Male Dogs
The main symptom of infertility is not really a "symptom," but instead is an outcome: the failure to produce puppies. Many of the causes of male infertility are painful, which contributes to their reluctance to mate. Other causes result in low or absent sperm production, which should not cause physical signs in affected males.
Loss of libido (sex drive)
Bloody urine (hematuria)
Difficulty urinating (dysuria)
Straining to defecate (tenesmus)
Enlarged, inflamed, painful testicles (orchitis; one or both can be affected)
Reluctance to sit
Stiff, stilted gait
Increased frequency and volume of urination (polyuria)
Increased thirst and water intake (polydipsia)
Small testicles (one or both)
Enlarged testicles (one or both)
The genitalia of dogs with intersex chromosomal abnormalities often look abnormal to the naked eye.
Dogs at Increased Risk
Old dogs have an increased chance of being infertile, as do dogs with certain hormonal and metabolic diseases. Dogs that are scolded or punished for exhibiting sexual behavior when they are not in a planned breeding situation are at an increased risk of being shy or reluctant breeders. Cryptorchid dogs with one or both undescended testicles are predisposed to being infertile, as are stud dogs that are overused. There is no reported breed predisposition to infertility in domestic male dogs.
How Infertility in Male Dogs is Diagnosed
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.
Treatment Options for Infertility in Male Dogs
Many of the causes of infertility in male dogs are potentially reversible. Treatment options will be discussed only generally here, because a detailed examination of all treatment protocols for each possible cause of canine infertility is beyond the scope of this article. For example, dogs with infertility caused by diabetes may need to have their diabetes treated with insulin and dietary management. Owners of diabetic dogs with fertility problems can review treatment options under the Diabetes Mellitus heading in the Pet Wave Dog Health Library.
A long period of rest, without sexual activity or exposure to temperature extremes, can restore moderate to normal sperm production if infertility was caused by prolonged exposure to heat, testicular trauma, stress or sexual overuse. Bacterial infection of the testicles or prostate can be treated with appropriate antibiotics, preferably following culture of the semen to identify the exact organisms involved. Hormone replacement therapy, and administration of certain medications, can be helpful for dogs whose fertility failures are caused by immune-mediated conditions, hypothyroidism, diabetes, hypgonadism or retrograde ejaculation.
In some cases, a retained testicle can be dropped into the scrotum surgically, although depending on its initial abdominal location it may or may not produce live sperm. Many breeders and veterinarians consider this procedure to be unethical if the owner intends to use the dog for breeding, because cryptorchidism is considered to have a genetic component. Surgery can also be used to correct a persistent penile frenulum and phimosis, so that the dog can have a normal erection. Sometimes, treating the underlying cause of infertility requires castration (neutering).
The semen of dogs with normal sperm counts that are reluctant to breed for whatever reason can be collected manually. The collected semen can be used or fresh, chilled or frozen to impregnate a bitch via artificial insemination. There are a number of techniques for these procedures and a number of ways to handle and store the semen, which stud dog owners can discuss with their reproductive veterinary specialist.
Dogs with congenital infertility, and also those that do not produce appropriate numbers of sperm or otherwise respond to medical therapy after 6 months of treatment, probably will never become fertile. On the other hand, when a successful pregnancy was prevented by poor breeding management and mistimed matings, the prognosis is generally quite good – once proper protocol is followed. Dogs with infertility caused by infection also have a good prognosis, if appropriate diagnostics and treatment are pursued.