Canine: Breeding soundness examination of the stud (Proceedings)

Indications for Karyotyping include possible testicular hypoplasia/aplasia, abnormal external phenotype (e.g. small penis, ambiguous genitalia), and suspected congenital lesions associated with infertility.

Herpes virus diagnosis titer determinations are indicated in animals suspected of being clinically affected or subclinical carriers of the virus. This virus can have serious effects on the newborn or cause abortions or stillbirths. It is of little concern once the canine neonate is 4 weeks of age.

Mycoplasma and Ureaplasma diagnosis depends on isolation of the organism from the ejaculate or from preputial swabs or urethral swabs. A pure culture may be interpreted as significant if isolated in association with inflammatory cytologic findings and clinical signs suggestive of the disease. Recovery of the organism in the absence of cytologic signs of inflammation or clinical signs consistent with infection, early embryonic death, fetal death, reduced conception rate, abortion, stillbirths, fading pups and neonatal deaths is likely to be due to contamination. The organism may exist in the prepuce without causing a problem. The same is true of finding the organism in the vagina. Interpretation of the finding of this organism as significant is difficult (or impossible) without clinical signs.

Endocrine testing is usually not indicated as it is in the bitch. Most of the subfertility problems encountered in the male are behaviorally related and not androgen dependent. Basal testosterone concentrations are difficult to interpret due to the wide variation in normal serum concentrations with normal intact male testosterone reaching castrated male concentrations periodically. The normal range is 0.5 to 10 ng/ml. The use of a GnRH of hCG stimulation test may provide more information regarding testosterone concentrations. Testosterone concentrations in intact and cryptorchid animals may be expected to rise to 3.7-7.5 ng/ml between 1-4 hours after GnRH (2 ug/kg IM for canine) or hCG (40 IU/kg IM canine).

Serum follicle stimulating hormone (FSH) concentration has been used as an indicator of spermatogenesis. In the presence of testicular lesions and reduced spermatogenesis, testicular inhibin production declines and FSH concentrations rise. The guidelines for FSH concentrations are: normal dog (20-130 ng/ml), active acute testicular degeneration (130-250 ng/ml), and severe testicular damage with depletion of seminiferous tubules (>250 ng/ml).

Luteinizing hormone (LH) concentrations may provide some information regarding the presence of lesions within the testes. In cases of testicular dysfunction LH concentrations tend to rise, probably due to increased GnRH release associated with increased stimulation of FSH and decreased leydig cell testosterone production associated with testicular damage. It is important to remember that the last functional part of the testis to be destroyed do to damage is the androgen producing tissue.

A complete physical should be performed to identify disorders of non-reproductive systems.

The physical examination should begin with scrotal palpation and must ensure the presence of two normal scrotal testes. The size of the testes should be recorded, as should be the symmetry and consistency. The epididymides, vas deferens and spermatic cords should be palpated for the presence of abnormalities. The penis and prepuce should be examined during the examination and usually is easiest performed at the time of semen collection. However, the penis should be palpated through the sheath in the unstimulated dog to determine in the non-erect state that it is normal. Following this, manipulation of the penis out of the sheath can be performed for closer examination of the penis and prepuce more closely. The os penis is examined by palpation through the penis for the presence of irregularities such as fracture of the os and congenital abnormalities.

Rectal palpation of the pelvis, pelvic urethra and prostate gland should be performed on all males at least once a year. Even neutered males should be examined due to the possibility of neoplastic lesions of the prostate. Palpation of prostate gland is facilitated by elevating the front end of the dog and using the free hand under the abdomen to elevate the prostate towards the finger inserted in the rectum. Palpation should detect changes in size, consistency and symmetry of the two lobes of the gland. An examination of the mammary chain by superficial palpation of the chain should be performed. A brucella test should be performed annually and a thyroid panel should be performed on all animals where indicated.

Semen collection and evaluation

Semen collection is accomplished by manual stimulation of the penis and semen is collected into a sterile latex or plastic cone connected to a sterile semen collection tube. A sterile non spermicidal lubricant should be used to avoid trauma to the penis and prepuce and injury to the sperm. The semen sample should be evaluated immediately after collection for motility. The sample should be kept at 37° C until after the motility evaluation and morphologic slides are made. All slides and cover slips should be at the same temperature as the semen sample. The color of the sample should be milky white. Abnormal coloration is usually due to contamination with urine, blood or the presence of white blood cells.

The volume of ejaculate collected is collected. This number will be necessary to calculate the total number of sperm in the ejaculate. The volume should be between 1.5 and 3.0 ml of the sperm rich fraction. The total ejaculate may consist of 30 ml but the majority of the volume is due to the prostatic fluid that is detrimental to the sperm and should not be collected.

Motility and debris are assessed by examination of a drop of ejaculate under a microscope.

The percentage of cells showing linear, progressive motility is estimated and recorded. One way to become proficient at estimating motility is begin by to evaluating 3 to 5 sperm at one time and determining what percentage is moving rapidly forward in a straight line. The average acceptable normal percentage of normal motile sperm is at least 70%.

Sperm concentration can be determined by hemocytometer, spectrophotometer or Coulter counter. There should be at least 200 X 106 sperm/ejaculate. The total sperm number ejaculated (volume x concentration) should be between 300 to 1,000 x 106.

Semen morphology is evaluated by mixing one drop of semen and one drop of eosin-nigrosin stain on one end of a slide and using another slide to make an even smear of stained cells. The technique is similar to the making a blood smear. The smear is air dried and examined under oil immersion and the proportions of normal cells and primary and secondary abnormalities is determined by counting 100-200 cells and reported as a percentage. Wet mount preparations can be used by mixing sperm with 10% buffered formalin and examining with a phase contrast microscope. The total abnormalities should be less than 30%.

Epididymal aspiration may be indicated if the dog has a palpable abnormality affecting one or both epididymides or if the ejaculate is azoospermic. This technique may aid in the diagnosis of obstructive lesions involving the outflow tract, neoplasia, sperm granuloma and epididymitis. It may be performed in the standing, sedated, or anesthetized animal. An area over the tail of the epididymis is prepared aseptically and a 23-25-gauge needle passed through the skin and into the epididymis and a small amount of contents aspirated into the needle and syringe.

Testicular biopsy provides information regarding the etiology of a testicular lesion and the severity of a testicular lesion and in prognosticating a return to normal function. It may be indicated in animals with oligospermia, azoospermia and high percentages of primary abnormalities in the ejaculate or a testicle that is abnormal in size, shape or consistency. Testicular biopsy can be performed with the patient, which is sedated, or under general anesthesia and in lateral recumbency. The methods for obtaining samples include excisional wedge resection, fine needle aspiration and split needle biopsy. The split needle biopsy technique is the preferred method by the author. The scrotum is clipped, prepared aseptically and a small incision made in the scrotal skin over the ventral surface of the testis near the cranial end, taking care not to involve the area of the head of the epididymis. The split needle biopsy instrument is passed into the testicular parenchyma, angling towards the caudal aspect of the testis and a sample taken and placed into 10% formalin or Bouin's solution for submission to a histopathologist. Samples are evaluated microscopically for the presence of germ and Sertoli cells, proliferation and maturation of germinal epithelium, spermatids within seminiferous tubule lumens, leydig cells and for the presence of lesions.