Page 550 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.2 The male reproductive tr act 525

VetBooks.ir Number of progressively motile, disease, and may be most useful for prognosis. The
typical hormonal profile in TD includes high FSH,
morphologically normal sperm
The calculation method is demonstrated in Table 2.4.
In stallions classified as satisfactory, the second ejac- low oestrogen and inhibin, and normal to low lev-
els of LH and testosterone. Oestrogen values below
ulate contains more than one billion PMMN sperm. <455 pmol/l [124 pg/ml] (suggest irreversible damage
to the seminiferous epithelium and a poor prognosis.
Longevity of motility
For raw semen, at least 10% progressive motility is Examination for venereal disease
anticipated after 6 hours when semen is held in a vial Examination for venereal disease includes visual exam-
in a 37°C (98.6°F) water bath. Poor longevity is asso- ination of the external genitalia and bacterial culture of
ciated with short sperm survival time in the mare’s the genital skin, pre- and post-ejaculatory fluids, and
reproductive tract. semen. The penile, preputial and scrotal skin is evalu-
ated for erosions, granulomas, tumours, masses and
Hormonal evaluation exudates. The testis and epididymides are palpated to
The addition of hormonal evaluation in a standard detect hard or soft areas and enlargements. After teas-
BSE is the subject of some controversy. In normal ing, cultures of the prepuce, shaft of the penis and ure-
stallions, where physical examination and semen thral fossa are collected. The erect penis is washed and
analysis are within normal limits, hormonal evalu- dried thoroughly using warm water and soft cotton.
ation is highly unlikely to provide any useful infor- Washing the genitalia in disinfectant soap is gener-
mation. Veterinarians managing stallions with large ally contraindicated to avoid overgrowth with patho-
books may elect to monitor hormonal status once or genic or resistant bacteria. After washing, the glans
twice yearly. When hormonal testing is done, sev- penis is massaged and the pre-ejaculatory secretions
eral samples on consecutive days should be taken to are swabbed by insertion of a sterile culturette into
avoid sampling in the trough of the normal pulsatile the urethra. If possible, semen for bacterial culture can
secretion. Baseline serum samples can be tested for be collected in an open-ended vagina to allow frac-
FSH, LH, oestrogens, testosterone and inhibin. In tionation but, in most cases, semen is collected using
stallions with abnormalities on physical examina- a regular artificial vagina and a sample of the ejacu-
tion or spermiogram, additional tests, including a late is submitted for semen culture. Immediately after
human chorionic gonadotropin (hCG) stimulation ejaculation, the urethral swab is repeated. In a normal
test (see p. 553) or GnRH challenge test, can be con- stallion, the second swab demonstrates a reduction in
ducted. Hormonal changes in stallions with testicu- bacterial populations compared with the first.
lar degeneration (TD) occur late in the course of the
Ultrasonography of the
male genital tract
The scrotal contents and spermatic cords are easily
Table 2.4 Number of progressively motile,
morphologically normal (PMMN) sperm evaluated using a portable ultrasound machine with
a 5- or 7-MHz linear probe. The testes are uniformly
Semen parameters echogenic, while the epididymes are comparatively
• Volume 50 ml hypoechoic and granular. Unilateral conditions can
• Concentration 100 million/ml be evaluated by comparison with the contralateral
• Progressive motility 70%
• Morphology 50% normal side. Biopsy of abnormal areas is facilitated by ultra-
sonography. Ultrasonography of a cryptorchid testis
Example calculation:
and the ampullae and prostate glands is performed
Volume × concentration × proportion motile × proportion transrectally. In addition, a cryptorchid testis can
morphologically normal also be examined by parainguinal ultrasonography.
50 ml × 100 million/ml × 0.70 × 0.50 = 1,750 million or Adequate restraint and sedation are required to min-
1.75 billion PMMN sperm
imise the risk of rectal tears.