Approaches to Poor Semen Quality
The ease of collecting semen permits a great opportunity to evaluate the male dog's reproductive function and provide information on the sight of any defects.
(i) Normal Semen Quality - Semen from a male dog is normally a cloudy white fluid, ranging in volume from 1 ml to 30 ml, containing 300 to 2,000 million sperm per ejaculate, of which more than 70% are motile and morphologically normal (i.e. structurally sound).
(ii) Failure to Show Normal Copulation - Poor libido results in failure to achieve an erection or ejaculation. It can be caused by inexperience, stress, inadequate testosterone levels in the blood, pain generated from an infected prostate, or back/hip pain which hurts the dog during mounting. Measurement of testosterone levels in blood is usually not helpful in diagnosing the cause of poor libido, but some dogs with poor libido respond to administration of gonadotrophic releasing hormones with improved libido within 1 to 3 hours.
(iii) Normal Erection but failure to Produce Sperm (Aspermia) - The cause of absence of an ejaculate includes retrograde ejaculation (i.e. ejaculation of sperm into the urinary bladder) and drugs or surgery induced sympathetic denervation of various male reproductive structures such as epididymis, vas deferens and prostate. If a dog shows normal libido, erection and ejaculatory behaviour but fails to produce a fluid ejaculate, a catheter is placed into the urinary bladder enabling examination of the bladder fluid for the presence of sperm. Retrograde ejaculation is confirmed if quite a large quantity of sperm is found.
(iv) Presence of a Fluid Ejaculate but Without Sperm (Azospermia) - Absence of sperm in a fluid ejaculate may be due to incomplete ejaculation, outflow obstruction of the male reproductive passages as epididymis or vas deferens, or failure of testicles to produce sperms. If ejaculate is found to have no sperm, a sample is collected and sent to a laboratory to test for semen plasma alkaline phosphatase levels so as to localise the cause of such condition. A low level (less than 100 IU/l) suggests incomplete ejaculation whereas a medium level (between 100 and 2000 IU/l) suggests an outflow obstruction. A normal level (above 5000 IU/l) indicates both complete ejaculation and patent male reproductive passages, and that the cause of absence of sperm in the ejaculate is testicular failure.
(v) Incomplete Ejaculation - Diagnosis is based on low semen plasma alkaline phosphatase levels and evidence that the dog has not completely ejaculated (e.g. fear, inexperience, absence of bitch in season). The best approach is to repeat the attempt to collect an ejaculate in a calm, quiet environment in the presence of a teaser bitch.
(vi) Outflow Obstruction - This may be caused by failure of parts of the epididymis or vas deferens to develop, or the development of a cyst or abscess in the epididymis. The semen plasma alkaline phosphatase level is usually 1000 - 2000 IU/l if the obstruction occurs in the epididymis. Ultrasound and culture of seminal plasma are the best ways to confirm the diagnosis.
(vii) Testicular Failure - Presence of normal semen plasma alkaline phosphatase levels (above 5000 IU/l) in a sample with the absence of sperm is suggestive of testicular failure. The causes of such failure include abnormal sex differentiation, use of drugs toxic to testicles, elevated levels of sex steroids, autoimmune inflammation of testicles, prolonged fever, testicle irradiation, infection, inbreeding, testicular tumours, or increased temperature inside the scrotum.
Drug induced testicular toxicity may occur after long term use of cortisone, testosterone or ketaconozole. Elevated levels of sex hormones can occur with certain tumours such as Sertoli Cell tumours whereas high levels of cortisone occur in Cushingoid dogs.
Autoimmune inflammation of testicles must be suspected in dogs that were previously fertile but now produce fluid lacking sperm. It is also suspected when there is testicular failure with normal semen plasma alkaline phosphatase levels and other causes of testicular failure have been eliminated. Diagnosis can often be confirmed upon biospy of the testicles.
Infection of testicles or epididymis is often painful and may lead to ejaculation failure when stimulated. Affected dogs have a high number of bacteria present in the ejaculate.
Overall it should be noted that the conditions in most azospermic dogs with normal semen plasma alkaline phosphatase level are irreversible.
(viii) Presence of Blood in Ejaculate - Unless there has been trauma to the penis at the time of semen collection, blood in the ejaculate is usually associated with enlarged prostate. The condition is normally not harmful to fertility in the absence of infection. However, the blood tinged ejaculate must be cultured to rule out infection as superimposed bacterial infection of the prostate is common in dogs with enlarged prostate.
(ix) Presence of White Blood Cells in Ejaculate - Normal male dogs have less than 2000 white blood cells per ul in the first two fractions of semen. Increases in number of white blood cells indicate the presence of infection and the ejaculate must be cultured. Canine semen infected with bacteria shows fairly consistent changes to the sperm such as reduced motility, increased number of sperm with defects and clumping of sperms. Prostate is the most common organ to be infected. Affected dogs are treated with appropriate antibiotics.
(x) Abnormal Sperm Morphology - The presence of more than 10% primary or 20% secondary abnormalities indicates an inherited defect since birth or acquired insult to the sperm secondary to fever, infection, trauma or other insults to the testicles. Secondary abnormalities are common with many causes of poor sperm quality such as infection, fever, cortisone use and autoimmune disease.
(xi) Below 25% Motile Sperms - A reduced percentage of progressively motile sperm is associated with fever, inflammation and infection. There are three main rule outs for causes of reduced sperm motility: contaiminated collection vial, presence of infected or inflamed exudate in semen, and rarely congenital cilia syndrome.
Semen with less than 25% sperm motility are cultured and a repeated ejaculate is collected in a different vial. Confirmation of the rare immotile cilia syndrome is made using a special microscope to look at the sperm tails.
(x) Less than 200 Million Sperms in Ejaculate - This infers a sperm count of 50 - 200 million. Dogs with such semen are sub-fertile. The condition may occur with infection or as a stage in the progression from normal sperm production to premature testicular failure. These dogs have a poor chance of fertility though small size litters are possible.