Page 562 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.2 The male reproductive tr act 537

VetBooks.ir precursor cells, and alkaline phosphatase (AP). until ejaculation occurs may be required. Retrograde
ejaculation may be treated with behaviour modifica-
AP levels >1000 IU/l indicate testicular and epididy-
mal secretions are present, confirming ejaculation
are detected, treatment is attempted using a trial and
has occurred. When retrograde ejaculation is sus- tion and imipramine. If no causative abnormalities
pected, the bladder is catheterised and high numbers error approach. In unresolved cases, testicular biopsy
of spermatozoa are found in the urine. In stal- to determine spermatogenic activity and cannulation
lions that do not ejaculate after multiple collection of the ductus deferens to determine patency can be
attempts, palpation and ultrasonography of the ure- performed surgically.
thra and accessory sex glands are performed. In the
normal stallion the ampullae are 1–2 cm in diameter, Prognosis
while in stallions with ampullary blockage they are In cases where a management issue is identified,
larger and very firm on palpation. Endoscopy of the such as incorrect phantom height or improper arti-
urethra and colliculus seminalis may reveal abnor- ficial vagina temperature, the prognosis is excellent.
malities such as inflammation, purulent discharge or Cases of ejaculatory failure caused by ampullary
physical obstruction. blockage can be difficult to resolve; however, after
resolution, stallions return to previous levels of fer-
Management tility. Blockage may reoccur after periods of sexual
Treatment depends on the cause of the ejaculatory rest, and therefore it is advisable to collect affected
dysfunction. Stallions with musculoskeletal and neu- stallions on a regular basis. In stallions where neu-
rological disease are treated with appropriate medi- rological or musculoskeletal disease is impairing
cations and modification of the breeding routine to ejaculation, function is improved by treatment;
facilitate stallion comfort. In stallions with ampullary however, the prognosis for long-term fertility is
blockage, administration of oxytocin and transrec- guarded. Aplasia of the excurrent duct system results
tal ampullary massage prior to collection may prove in untreatable infertility.
curative. Repeated collection attempts 2–3 times daily

CONGENITAL ABNORMALITIES OF THE MALE REPRODUCTIVE TRACT

DISORDERS OF SEXUAL Aetiology/pathophysiology
DEVELOPMENT (INTERSEXUALITY) A number of disorders of sexual development (DSD)
result in phenotypic ambiguity, including mono-
Definition/overview somy X (Turner’s syndrome), XXY syndrome
The normal genotype of the horse is 64XX or 64XY. (Kleinfelter’s), mosaicism, gene translocations and
The term intersex is used to describe an animal with a receptor deletions. The presence of the SRY gene on
sexually ambiguous phenotype. Several variations of the Y chromosome controls a cascade of events and
intersexuality occur in the horse. True hermaphro- testicular-secretory factors that in turn control the
dites have both testicular and ovarian tissue present. development of the internal and external genitalia.
Sex reversal is used to describe an animal in which the Historically, translocation of the SRY gene from the
genetic sex disagrees with the gonadal sex (e.g. 64XX Y chromosome onto an autosome was thought to be
individual with testes). The term pseudohermaphro- responsible for intersex conditions in most cases.
dite is used to describe an animal in which the genetic Absence of the SRY gene in genetic males results in
and gonadal sex agree, but the presenting phenotype failure of regression of the müllerian ducts, which
is in disagreement. A male pseudohermaphrodite is form the female tubular tract, since müllerian-inhib-
64XY with testes and female- appearing genitalia. iting substance and other factors are not secreted by
A female pseudohermaphrodite is 64XX with ovaries the Sertoli cells. In SRY-positive cases of XY sex
and male-appearing genitalia. reversal, failure of androgen receptor expression on