| Infertility in the Dog |
| Dogs are usually presented for evaluation of infertility because of unwillingness or inability to breed, or because bitches bred by them have failed to whelp. Often it is unknown if the lack of whelping represents failure to conceive or if conception was followed by embryonic death, because early pregnancy diagnosis is not always performed. The recommendation to evaluate a dog for infertility when pregnancy/whelping rates are less than or equal to 75%: 1. or when 3 consecutive bitches have failed to become pregnant. 2. is certainly applicable for a dog in a very active breeding program, wherein 3 negative breedings or a decline in pregnancy rate to 75% would become apparent in a matter of weeks or months. However the less frequently a dog is used a stud, the longer the time before infertility is recognized. Waiting to evaluate male fertility until 3 consecutive, or 3 of 4 (75%), bitches have failed to whelp may be counterproductive in some circumstances because, in the meanwhile, fertility may be progressively worsening. Declining litter size is also a sign of infertility, but it is unlikely to be recognized in a male that is infrequently used at stud. Optimal male fertility requires nonrmal libido, normal mating ability and normal semen quality. The relative contribution of the bitch to the outcome of breeding must also be considered. To further complicate matters, dogs and bitches are rarely left to breed on their own. The timing and frequency of insemination, and the type of semen (fresh, chilled, frozen) are determined by the owner. The history should assess the dog's general health, including vaccination and Brucella canis status, illness in the dog or kennel-mates, medications, and concurrent strenuous activity such as hunting or endurance racing. Specific questions should be asked to assess the dog's libido, such as his apparent degree of arousal and interest in the bitch, and his desire to mount. Was the bitch apparently receptive? Once mounted, did vigorous pelvic thrusting and intromission occur? It is often difficult to differentiate physical from psychological factors, and male factors from female factors, when assessing libido. For example, bitches that are not in estrus will not demonstrate complete receptivity. Likewise, some males are not as aroused by bitches not yet in estrus. Libido declines in old dogs. Inexperienced or subordinate males may be deterred by a dominant bitch or unfamiliar surroundings. We have observed the occasional dog that temporarily exhibits poor libido apparently soley as a result of exhaustion from prolonged strenuous acivity. Physical abnormalities of the bitch, such as vaginal septum, or the dog, such as orthopedic problems, may preclude normal mounting and/or intromission, despite normal libido. Conversely, this may be misinterpreted as poor libido. Any painful condition, including that of the prostate, may adversely affect libido and mating ability. Did a post-coital tie or lock occur when the dog dismounted? Dog semen is ejaculated in three fractions. Discharge of the first fraction, which originates from the prostate, begins during the time of rapid pelvic thrusting. Thrusting generally stops as ejaculation of the sperm-rich(second_ fraction begins. Ejaculation continues, primarily of the third fraction (prostatic fluid), during the post coital tie. Although the duration of the tie does not influence conception, the fact that it occurred confirms that intromission was achieved, and that vaginal deposition of any ejaculate most likely occurred. In the absence of a post-coital tie, neither intromission nor vaginal insemination can be confirmed. A dog that is highly aroused and completely erect will be unable to achieve complete intromission because the bulbus glandis has become too large. In this situation, a tie will not occur when the dog dismounts. Dog breeders may refer to this situation as an "outside tie". Ejaculation may have occurred, but not necessarily intravaginally. The dog's previous breeding record should be evaluated to determine his pregnancy/whelping rate over time. Whether the bitches became pregnant when bred to other males before and/or after this dog is of interest. The frequency with which the dog is used at stud may be important. For example, daily ejaculation will cause a dramatic, but not necessarily clinically significant, decrease in the number of sperm in each ejaculate. The methods by which the dates for breeding were chosen should be reviewed to determine if the inseminations likely occurred during the optimal fertile period. Compared to a single insemination, two breedings during the fertile period result in imroved pregnancy rates. The method of insemination, natural service versus vaginal or intrauterine artificial insemination is also important. A complete, thorough physical examination should be performed for two important reasons. The first is that systemic illness, and/or the treatments thereof, may adversely affect male fertility. The second is that potentially heribable conditions may be detected. Heritable defects may make a dog undesirable as a stud and preclude additional fertility evaluation. When the history suggests poor libido or poor mating ability, the dog should especially be evaluated for musculoskeletal and neurologic disorders common to the breed. The reproductive tract is then thoroughly examined. The prepucial and scrotal skin are inspected. The scrotal contents are carefully palpated. The testes, epididymes, and spermatic cords are assessed for normal location, size, shape, consistency, and discomfort. The testes and epididymes are smooth. Typically, the tail of the epididymis is slightly more firm than is the testis. The epididymis can easily be differentiated from the testis, especially along the tail. When the epidiymis and testis cannot be differentiated from one another by palpation, one or both is abnormal. Testes that are softer or smaller than normal may not have normal spermatogenesis. The width of each testis, and the total scrotal width can be recorded. This is accomplished by gently pushing the testes to the bottom of the scrotum and measuring the width across the caudal aspect. The testes should be evenly aligned in the saggital plane when the total scrotal width is determined. The results are helpful in monitoring progression, or resolution, of disease. The causes of abnormally small testes include congenital hypoplasia, degeneration and atrophy. Consequently, the prognosis for recovery of fertility in dogs whose testes are already abnormally small is grave. A possible exception might be testicular atrophy that is the result of suppression of the hypothalamic-pituitary-gonada axis, as could occur with excessive estrogen and other endocrine events. Testicular tumors of sufficient size are easily palpable. They are usually somewhat irregular and of different consistency than the surrounding parenchyma. When a unilateral testicular disorder, such as orchitis or tumor, is found hemi-castration should be considered to protect the normal testis from damage from the heat, pressure, direct extension, or hormaonal effects of the affected testis. If the history suggests a penile problem, the penis should be examined before semen collection is attempted. Otherwise, the penis may be examined during semen collection. The prostate is best examined with both hands, by simultaneous transrectal and transabdominal palpation. Relative to the smooth testis, the surface of the prostate is slightly textured. The prostate is bi-lobed and symmetrical. Palpation should not elicit pain. Abnormalities found during physical examination should be addressed. A CBC, biochemical profile and urinalysis would be reasonable to assess the dog's overall health. However, in the absence of physical abnormalities or overt signs of illness, these are unlikely to discern a cause of infertility. Screening infertile dogs for hypothyroidism is usually recommended. However, it has been shown that experimentally-induced hypothyroidism has no adverse effect on libido, testicular size, daily sperm production, semen quality, or serum concentrations of testosterone and LH in adult dogs. Ultrasound is an excellent method to further evaluate any abnormalities found during palpation of the scrotum, spermatic cord, testes and epidiymes. Ultrasound is superior to palpation for evaluating the prostate. Prostatic disease is often cited as a cause of infertilty. Fine needle aspiration under ultrasound guidance of testicular and prostatic lesions is easily performed. Samples are submitted for appropriate cytologic and microbiologic evaluation. Ultimately, the single most important determinant of male fertility is semen quality. Poor libido and poor mating ability can be cirumvented by assisted reproductive techniques such as electroejaculation and artificial insemination. Semen should be collected and submitted for cytologic evaluation and culture as previously described. The number of sperm, their morphology and motility, and the presence of other cells are the major parameters asscessed. The results can be categorized as normal, oligozoospermia, azoospermia, teratozoospermia, asthenozoospermia, leukospermia, and hemospermia. The dog is normal...In this situation, first the breeding management should be investigated. A minimum of 2 breedings should occur during the optimal fertile period, as determined by ovulation timing. If AI was used in the past, the technique should be scrutinized to insure that the semen is not damaged during collection and or insemination. Pregnancy rates for frozen semen are improved with intrauterine, rather than intravaginal, deposition. The quality of chilled or frozen semen is affected by the composition of the media; the method of dilution (one step or two); the final concentration of sperm; and the temperature and rate of cooling, freezing and thawing; and the temperature of storage. Thus normal semen could be damaged anywhere during collection, the chilling or freezing process, storage, transport, warming or thawing or insemination. The second consideration for a normal dog with normal semen is to investigate the fertility of the female, or simply breed to a different female, preferably one known to be fertile. The third consideration is that the dog has recovered from previous infertilty. Whenever one specimen of abnormal semen quality is found, the dog should first be re-evaluated. If the semen quality is again abnormal, an aliquot should be saved or submitted for culture while additional workup is underway. Morphologically abnormal sperm often do not have normal motility. Morphologic and motility abnormalities can be iatrogenic, as a result of cold or heat shock, and abnormalities in PH or osmolality. Normal sperm have rapid, steady, forward progression. Iatrogenic causes are the most common reason for poor motility in morphologically normal sperm. However, decreased motility is also one of the early signs of testicular damage. Teratozoospermia and asthenozoospermia are expected in sexually immature and geriatric dogs. The number of abnormal sperm may increase and motility decrease after a period of abstinence because of normal senescence of sperm in the extra-gonada sperm reserves. If only a small volume was collected, the presence of abnormal sperm must not be over interpreted. Instead, a sample from the dog should be collected again. Decreased vigor of movement that is otherwise normal is often a sign of cold. If so, a second aliquot from the sample, allowed to equilibrate to 37 degrees on a warm slide, should have normal motility. Sperm that are moving backward, in circles, or otherwise abnormally usually do so because morphologic defects in the midpiece or tail prevent them from moving in a straight, forward manner. Morphology is categorized according to head, midpiece and tail abnormalities. Inappropriate PH or osmalality of the stain can create abnormalities. When the motility is normal, yet excessive tail and midpiece abnormalities are found, an iatrogenic cause, such as a problem with the stain, should be suspected. Any insult to the testis can result in teratozoospermia. Recovery is possible if the spermatogonia are not irreversibly damaged. In normal and abnormal semen there are usually a variety of morphologic abnormalities in a given sample. Based on observations in bulls, when a single morphologic abnormality predominates over all others a genetic (heritable rather than acquired) basis is suspected, especially if the single morphologic abnormality constitutes >25% of the sperm in a sample and is a persistent finding. Two such defects, the Dag defect and "tail stump" defect, have been identified in individual dogs whose semen quality fit the criteria for genetic defects. Some morphologic abnormalities, such as distal droplets and otherwise normal detached heads, have relatively little impact on fertility in dogs unless there are also less than or equal to 60% normal sperm in the sample. This type of abnormality has been referred to as "compensble", because increasing the number of functionally normal sperm inseminated should compensate for, or overcome, the problem. Other sperm defects, such as detached normal heads, and double tails, have been described as major defects in the dog. These may be uncompensable. The number of sperm produced is directly related to testicular size. Although the prognosis for oligozoospermia is obviously better than for complete lack of sperm, the diagnostic considerations are initially the same. Sexually immature and geriatric dogs are expected to have oligo- or azoospermia. In normal dogs, daily ejaculation will decrease the number of sperm in each ejaculate by depleting the extra-gonadal sperm reserves in the epididymis and ductus deferens. Very few sperm are present in a second ejaculate on the same day. To maximize the number of sperm, there should be 3-4 days between ejaculation. Dogs with oligozoospermia may not replenish the sperm reserves as quickly as normal dogs. Small numbers of otherwise normal sperm can still result in pregnancy. Chances will be improved when insemination is performed during the optimal fertile period, as determined by ovulation timing. |