Infertility

28 Infertility




Infertility in male dogs can occur from many causes (Figure 28-1). If the male is not capable of mounting and breeding the bitch, physical or behavioral problems may be at fault (Figure 28-2). If he is capable of breeding the bitch and has normal semen quality, appropriate timing of breeding should be investigated. Inappropriate breeding timing is by far the most common cause of apparent infertility in dogs (see Chapter 9). If he has normal semen quality and breeding management has been adequate, possible causes of infertility include prostate disease (see Chapter 26), brucellosis (see Chapter 20), testicular neoplasia (see Chapter 25), and genetic incompatibilities with the female.




If the male is capable of breeding the bitch but does not have normal semen quality, as determined by semen evaluation, specific causes for poor semen quality must be addressed (Figure 28-3). Although abnormalities of spermatozoa will be described as separate entities, be aware that often a single problem will cause multiple abnormalities; for example, anything that causes an increase in abnormally shaped spermatozoa is likely to cause a decrease in percentage motile spermatozoa because the abnormally shaped spermatozoa are unlikely to have normal motility.



Aspermia is lack of any ejaculate. Possible causes include apprehension and pain at the time of ejaculation. Some very experienced male dogs will not ejaculate in the absence of an estrous teaser bitch. Some other dogs have poor libido and are difficult to collect from even if an estrous teaser bitch is present. Dogs used for breeding or semen collection more than once daily have a rapid decline in libido. Dogs used daily have a slow decline in libido. Dogs used every other day do not show a change in libido from use. Low concentrations of testosterone in blood never have been identified as a cause of poor libido in dogs. Despite this, some dogs more readily ejaculate one hour after administration of gonadotropin-releasing hormone (GnRH), which presumably increases testosterone secretion. This should not be performed routinely as it may, over time, decrease spermatogenesis.


Azoospermia is lack of spermatozoa in the ejaculate. The dog ejaculates clear fluid. Causes can arise from before the testis, at the testis, or after the testis. Causes from before the testis include apprehension, hypothyroidism (see Chapter 6), and drug therapy that decreases spermatogenesis (Table 28-1). Causes from the level of the testis include abnormalities of sexual development (Figure 28-4), bilateral cryptorchidism (see Chapter 25), high fever in the previous 2 months or earlier, trauma in the previous 2 months or earlier, and testicular neoplasia (see Chapter 25). A cause arising after the testis is bilateral is occlusion of the epididymis. Testing of dogs with azoospermia usually starts with measurement of the enzyme alkaline phosphatase (ALP) in the sperm-free fluid collected by ejaculation. ALP in seminal fluid arises from the epididymis. If the concentration of ALP is low in seminal fluid, that suggests that no fluid was collected from the testes and the dog may well be capable of making spermatozoa. If the concentration of ALP in seminal fluid containing no spermatozoa is high, that suggests that the ejaculate does contain fluid from the testes and epididymes and prognosis is worse for return to function.


Table 28-1 Drugs Associated with Decreased Spermatogenesis in Male Dogs



























Drug Class Specific Drugs
Glucocorticoids (steroids)

Anabolic steroids ā€”
Estrogens

Androgens Testosterone
Progestogens Medroxyprogesterone acetate
Chemotherapy drugs ā€”
Antifungal drugs
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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Infertility

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