Introduction - a review in brief
The normal male dog attains puberty at approximately 6 – 8 months of age. Sexual maturity is generally attained at 18 – 30 months. Males may successfully breed bitches prior to sexual maturity but they will not achieve maximal fertility or daily sperm output until mature. The normal male can breed once every 2 - 5 days and maintain daily sperm output.
A complete breeding soundness examination in the dog includes history-taking, general physical examination, reproductive system examination, libido determination, semen collection and evaluation, hormonal evaluation, and prostatic examination and testing for disease (eg. Brucellosis).
In addition to artificial insemination breeding, collection of semen is indicated for evaluation in conjunction with a breeding soundness examination, in the diagnostic workup of potentially subfertile or infertile dogs, in the diagnostic workup of reproductive tract disease (infectious, degenerative or neoplastic disease), or for short-term (fresh-chilled extended semen) or long term (frozen semen) storage of gametes to be used in the future. When very young (< 7 months) or aged (>12 years) sires are used for breeding, the American Kennel Club (AKC) requires documentation, including a semen evaluation, of the male's ability to sire a litter.
The collection process - tips for success
• Ambiance is important. In the typical setting, ejaculation in the dog is a voluntary process and cannot be forced or rushed. The dog needs to be relaxed and comfortable with the place and the people involved.
• Be prepared. Have all supplies and adequate personnel available. You will need a dog handler, a bitch handler, a estrous teaser bitch (optimally), collection cones, nonspermacidal lubricant, 15-ml conical centrifuge tubes, a microscope, microscope slides, coverslips, bulb pipettes, stain, a means to determine sperm cell concentration (hemacytometer or Spermacue™) and other supplies depending upon the purpose for the semen collection. Some males may not require any external stimulus beyond manual massage to attain erection. If a teaser bitch is not available, many dogs will respond favorable to swab scent from an estrous bitch. Swabs can be collected and saved ahead of time.
Perform the collection on a non-slip, dog friendly surface (I have non-slippery epoxy flooring and my "magic carpet").
• With the bitch adequately restrained, the dog is allowed investigate the bitch's hindquarters. He may sniff or lick her external genetalia or rear limbs. He may or may not mount the bitch. Signs of readiness include salivation and "chomping" of his teeth. During collection, the dog should be observed for ease of achieving an erection, presence of a normal erection, normal thrusting behavior and normal pulsation associated with ejaculation and prostatic fluid emission.
• It is important to be aware of the onset of penile erection. Some males will achieve erection without any manual manipulation. Other males require brisk massage of the bulbus glandis through the prepuce to elicit erection. As soon as erection begins, the prepuce is moved proximally such that the entire prepuce is proximal to the exposed bulbus glandis. Failure to reposition the prepuce at the correct time may result in an inability to slide the prepuce proximally over the bulbis glandis. The collection process may then become painful to the dog as the skin of the prepuce tightens over the engorged bulbis glandis. It is important to roll over the edge of the cone such that the edge of the cone does not come into direct contact with penis. Failure to do so may result in a "paper cut" type of injury to the penis.
• Concurrent with prepucial positioning, the collecting cone is introduced over the engorging penis. The collecting cone covers the penis to the level of the bulbis glandis.
The collector uses his or her thumb and finger to form a ring proximal to the bulbis glandis and pressure is applied to the penis circumferentially, thus simulating the copulatory lock or "tie."
• With the onset of ejaculation, dog will thrust vigorously for several minutes. During this period, the first and second seminal fractions are ejaculated. The first or pre-sperm fraction is of prostatic origin and is clear. The pre-sperm fraction arises from the prostate and urethral glands, and is believed to cleanse the urethra of contaminants (urine, bacteria and cellular debris) prior to ejaculation The second or sperm-rich fraction originates in the cauda of the epididymis where spermatozoa are stored.
• After a brief period of rest, the dog will ejaculate the third seminal fraction. The third fraction is comprised of prostatic fluid and is normally clear. Prostatic secretion provide volume to the ejaculate, assist in propelling the sperm out of the vagina and into the cervix/uterus, and provide nutrients for the sperm while traveling to the site of fertilization in the oviducts. During third fraction collection, the dog may try to step over the collector's arm. If this occurs, the collector should lift the dog's rear limb over his or her arm and redirect the penis caudally to simulate the copulatory lock or "tie." It is important to redirect the penis caudally while maintaining the horizontal plane of the penis. Do not redirect the penis caudally in a vertical "pendulum swing" plane as this may cause injury.
• During ejaculation of the third fraction, the collector can feel and visualize the rhythmic pulsations in the penile urethral and perineal muscles. There is also an audible spurting of prostatic fluid into the receptacle.
• For breeding purposes, usually only the second, sperm-rich fraction is collected. If all three fractions of the ejaculate need to be collected, it is advisable to collect the fractions into separate receptacles. Fractionating requires the use of funnels or additional cones, dexterity and quick hands.
• Once semen collection is completed, the collector releases the penis and removes the collection cone. The dog often will continue to ejaculate pulses of prostatic fluid. Detumescence of the penis may require several minutes and often takes a similar amount of time as would recovery from a natural mating. Care should be taken to ensure that no injury occurs to the penis at this time.
• Make sure that subsidence has occurred and that the prepuce is positioned normally over the penis before allowing the dog to be discharged. Occasionally the prepuce rolls inward as penile engorgement wains leaving the unprotected glans of the penis vulnerable to dessication and trauma. With the aid of lubricant, the prepuce can readily be manipulated over the tip of the penis.
• Number of spermatozoa collected is optimized in the presence of an estrus teaser bitch. As much as a four-fold increase in spermatozoa number can be realized when using a teaser bitch. Alternatively, swab the perineum of any tractable female with frozen-thawed swab scent from an estrus bitch.
• For reticent dogs or when a teaser bitch is not available, semen collection may be facilitated by the administration of prostaglandin F2 alpha (Lutalyse®) at a dosage of 0.1 mg/kg subcutaneously 15 minutes prior to collection. Side effects commonly associated with prostaglandin administration (salivation, emesis, etc.) are minimal at this dosage.
• For breeding purposes, usually only the sperm-rich second fraction of the ejaculate is collected.