Evaluation of canine semen is an important part of the fertility workup in dogs. Unlike eggs, which are present at birth in the female, sperm cells are continuously manufactured throughout the male’s life. The health of the sperm is affected by the health of the male, and illness can make a dog infertile for a period of time. Therefore, semen evaluation is recommended for any important breeding, even if the dog has sired many litters in the past.
Semen collection & evaluation enables us to check the sample for the following :
- Volume: the volume collected affects the fertility in that a lower volume can contain fewer sperm.
- Clarity: sperm cells make the semen look milky. If the semen collected is completely clear, there are no or very few sperm present.
- pH: is the relative acidity/alkalinity of the semen. A value that is significantly out of the normal range can help the doctor to identify underlying causes of infertility.
- Progressive Forward Motility (PFM): is expressed as a percentage. A drop of the semen is placed on a warmed slide and examined under the microscope. PFM is an estimated percent of the visible sperm that are moving forward in a coordinated manner. This is as opposed to those which are not moving, or are just moving in place. Only sperm with good progressive forward motility will be able to fertilize an egg.
- Speed: the sperm with PFM are scored on a scale of 1 – 5 for speed. Slow-moving sperm may not be able to fertilize an egg.
- Count: the sperm count is measured both as a concentration of sperm per milliliter of semen, and as a total count for the entire volume of collected semen. Dogs with low sperm counts have reduced fertility.
- Morphology: Morphology refers to the physical appearance of each sperm cell. The cells are stained and examined under the microscope. Sperm cells are counted up to 100, keeping count of the number of normal vs. abnormal shapes. The abnormally-shaped cells are classified by type, and this can be very useful in determining the cause of infertility. In addition, any non-sperm cells are noted, such as white blood cells or red blood cells.
Together, this information is used to decide whether a dog is currently fertile, why conception might have failed, or how best to use the semen from an individual dog. For example, if the count is low but the sperm is of good quality, then this dog might best be bred using surgical insemination.
Semen evaluation is performed either in advance of, or at the time of a breeding. It is especially important when semen is to be chilled for shipment, and is mandatory if the semen is to be frozen. If a male has good PFM prior to chilling or freezing, but reduced PFM afterwards, sometimes we can use a different extender to improve the outcome.
If there is reduced PFM after chilling, a chill test can be performed. For this test, the dog is collected, the semen is evaluated, and then it is divided into several portions. Each portion is chilled in a different type of extender, and placed in the refrigerator. Every day, one drop of each portion is warmed and re-evaluated. This continues until the last portion has ceased to have PFM. This test enables us to determine which extender is best for the given stud dog. It is not commonly needed, but can be critical in certain cases.
Semen evaluation is recommended in advance of each important breeding, especially if it has never been performed before, the male has never sired a litter, the male has not been bred recently, or you are planning to freeze semen. If a male has not been collected or bred in many months, the semen quality can be improved by collecting a few times over a couple weeks.