Semen is often collected from dogs in a venue strange to them, or from inexperienced dogs. Therefore, it is good to have a bitch in season during semen collection to aid semen production from the stud dog as the stud dog may not produce semen in the absence of such bitch.
There are several reasons for semen evaluation.
(i) To ensure a young stud dog about to begin a stud career has normal sperm production.
(ii) To investigate infertility problems.
(iii) To monitor the production of sperm after an illness or drug therapy ensuring the dog is still fertile.
(iv) To look at the effect of prostate disease, if any, on semen quality.
(v) To assess the semen as part of an artificial insemination or frozen semen program.
Ideally the teaser bitch is restrained by the head or neck during semen collection and the dog is allowed to sniff the bitch's vulva. Once the dog is interested the penis is held and the prepuce is pushed backward so the whole glans ('bulb') is exposed. The glans is stimulated until the penis becomes erect. Normally the dog begins producing ejaculate during the initial violent thrusting - this ejaculate is clear and sperm free and does not need to be collected. Following this the dog produces the second fraction which is the sperm rich fraction. This fraction is collected. The sperm rich fraction is followed by a third clear fraction which is often collected to wash the sperm rich fraction into the collecting vial.
A sample of semen is evaluated after collection. During evaluation the sample is kept warm as cooling will reduce sperm motility and give a false impression of the semen quality.
Parameters to be Evaluated
Colour - Milky colour is normal. Any blood tinge is noted as blood may kill the sperm. If the semen collected is clear, it may indicate poor quality or no sperm production.
Sperm Motility - The assessment is made by placing a drop of semen on a warm slide and evaluating the percentage of sperm swimming actively under microscope. The semen sample is examined immediately as motility decreases with time.
Sperm Morphology - Approximately one hundred sperm in the drop of semen sample are examined and classified as either active, dead or abnormal. The dead and abnormal sperm may show abnormalities in head, neck, mid piece and/or tail.
Sperm Concentration - A semen sample is diluted at 1/200 with water and placed in a counting chamber. The number of sperm in specific squares of the chamber are counted and the sperm concentration in the semen is then calculated.
Total Sperm Output - This is calculated by multiplying the concentration of sperm (per ml) in the sample by the total volume of semen collected.
What do the Results of Semen Evaluation Mean?
Sperm Motility - Sperm in the semen of most fertile dogs have motility of 90 - 95%. Cases below 80% motility may be an indication of reduced fertility.
Sperm Morphology - Examples of abnormalities include the presence of many 'knobbed head' sperm which indicates sterility, presence of 'proximal cytoplasmic droplets' in the sperm neck region which indicates immaturity, and abnormal sperm tail which affects penetration into the egg cell during fertilisation. Any less than 80% normal may be an indication of reduced fertility.
Total Sperm Count - Anything more than 100,000 are compatible with good fertility.
Red Blood Cells in Semen - Red blood cells are commonly seen in semen samples collected from dogs over 5 years old. They originate from the prostate gland (even when there is no prostate disease). Large quantities of red blood cells do not appear to affect sperm motility.
White Blood Cells in Semen - White blood cells in semen usually originate from the side of the penis or lining of prepuce. They also indicate the presence of prostate disease.
How Can we Predict Fertility?
Semen quality is usually evaluated to be 'falsely' poor if semen is collected from an ill at ease dog, or the second collection on a particular day. Semen evaulation must be repeated another day before fertility can be predicted.
Semen quality may be severely affected if the dog has been on medication at the time of semen collection. A further sample must be collected following completion of the medication before fertility is assessed.
Dogs with good semen quality on evaluation are fertile and if mated with a bitch close to ovulation should produce offspring.
Dogs with poor semen quality (i.e. poor motility, abnormal sperms, low number of sperm) are often still fertile but mated bitches may be expected to 'miss'. Repeated mating around the time of ovulation may increase the chance of the bitch conceiving.
Absence of sperm or presence of small quantities of dead or abnormal sperm in the semen sample indicate the ejaculation has not been undertaken correctly or that the dog may have been treated with anabolics. Normal ejaculate will be produced two months after the anabolics are ceased.
Other cases that show no sperm or only a small quantities of sperm indicate that the sperm production has been arrested. These dogs were usually initially fertile but since have suffered a rapid asymptomatic degeneration of testicles resulting in the permanent absence of sperm and hence fertility.