SEMEN EVALUATIONS: What is normal?

By Debra Eldredge, DVM (as seen in IAMS Breeder Select News – Fall 2002)


If you own a stud dog, you may periodically want to have his semen collected and evaluated by your veteri­narian. A good semen evaluation provides breeders with confidence that their male can successfully impregnate females. How is the semen evaluated once it's collected, and what is considered "normal"?


Semen has three fractions or parts. The first fraction of the ejaculate, called the pre-ejaculate fluid, ranges in volume from 0.1 to 1.0 ml. The second part is the sperm-rich fraction, which is generally from 0.1 to 6 ml, depending on the size and breed of the dog. The third fraction is the prostatic fluid, which normally ranges from 1.0 to 20.0 ml.

Evaluation of a semen sample includes assessment of color; sperm motility, concentration, and morpholo­gy; and, the presence of other ceOs or bacteria.


Color: Healthy canine semen should be pearly white or translucent in color. Yellow semen indicates urine contamination, and urine is toxic to sperm. Red dis­coloration indicates that blood is present either from trauma, prostate problems or infection.


Sperm Motility: Since sperm have to be able to trav­el up the bitch's reproductive tract toward her eggs, the measure of how well sperm are moving and in what direction is important. A reading of 70% or greater motility is rated very good, 30% - 50% motility is fair, and 10% - 30 % demonstrates poor motility. Sperm should be moving rapidly forward, not in circles.


Concentration: The number of sperm in the ejacu- 250 million or more is desirable, especially if you are late determines its concentration. The more normal planning on freezing the semen. Dogs with lower con­sperm present, the better. Normal sperm counts can centrations can still get bitches pregnant, but higher vary from 1 million to over a billion per ejaculate, but counts increase the probability.

Morphology: Morphology is the evaluation of the structure of the individual sperm. Sperm have three parts: the head, which has a cap called an acrosome; the mid-piece, the location of the mitochondria or energy source; and, the tail. All three are important-the head for the genetic material, the mid-piece for energy to move and the tail to propel the sperm up the repro­ductive tract. Abnormal structure in any part may affect sperm movement or function. To be considered normal, a minimum of 80% of the sperm should have normal morphology.


Other cells or bacteria: The final consideration is to look for cells and bacteria in the semen sample. Normally there are few cells seen in an ejaculate; how­ever, certain prostatic diseases may cause high numbers to be present. Excessive bacteria may indicate the pos­sibility of infection, either in the testicles or the prostate.

If your dog gets a poor semen evaluation, don't despair. Many factors, including environmental tem­peratures and medications, can cause a poor semen evaluation. Correct any influencing factors and recheck the semen in about 60 days. .