Page 561 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

536 CHAPTER 2

VetBooks.ir intromission. Most stallions have normal libido, Abnormalities of the excurrent duct system, such as
blocked ampullary glands, can also prevent ejacula-
although those that have experienced repeated failed
breeding attempts may show poor libido or frus-
ting in the artificial vagina also may result in failure
trated breeding behaviour. tion. An inappropriate temperature or pressure set-
of ejaculation.
Diagnosis
Diagnosis is based on history and examination of Clinical presentation
the external genitalia. In cases where a cause is not Presenting complaints include inability to obtain
evident, breeding behaviour is observed and physical spermatozoa after collection with an artificial
and neurological examinations are performed to rule vagina, absence of urethral pulsing or tail flagging
out contributing conditions. at breeding, or a sudden decline in pregnancy rate in
mares bred by natural cover. Affected stallions usu-
Management ally show good libido and normal erectile function.
In cases where erectile function is permanently Stallions subjected to a cool artificial vagina often
impaired but testicular function is normal, the goal will continue to thrust, then stop and lose interest.
is to develop a protocol for reliable semen collec- Conversely, stallions subjected to an artificial vagina
tion. Training stallions to ejaculate through manual that is too hot will often back out of the artificial
stimulation and application of hot compresses to the vagina quickly, failing to ejaculate. Cases caused by
base of the penis is frequently successful. Chemical musculoskeletal or neurological disease may adopt
ejaculation may be attempted using imipramine atypical mounting positions, tread and readjust the
(2 mg/kg p/o) followed 2 hours later with xylazine hind feet, dismount after two or three thrusts and
(0.66 mg/kg i/v). This combination induces ejacu- have a worried or painful expression. Stallions with
lation within 20 minutes in approximately 50% of ampullary blockage show normal libido and pelvic
attempts. With either method, exposure to oestrus thrusting, but urethral pulsation, tail flagging and
mares in a distraction-free environment and spend- ejaculation do not occur. Occasionally, a stallion will
ing adequate time teasing will lower the ejaculatory present that appears to ejaculate normally; however,
threshold, increasing the likelihood of success. few or no spermatozoa are present in emitted fluids.

Prognosis Differential diagnosis
Stallions with chronic erectile failure due to physi- Differential diagnoses include severely impaired
cal abnormalities have a poor prognosis for recovery spermatogenesis, retrograde ejaculation, aplasia of
and a fair prognosis for fertility. the excurrent duct system and azoospermia.

EJACULATORY DYSFUNCTION Diagnosis
Differentiation of causes of ejaculatory dysfunc-
Definition/overview tion begins with a complete physical examination to
Ejaculatory dysfunction is defined as failure to ejac- detect arthritis and neurological disease. Palpation
ulate. Any cause of abnormal sexual function will of the external genitalia is performed to detect
result in a stallion that fails to ejaculate as reliably excurrent duct abnormalities, testicular atrophy
and quickly as desirable. Stallions with true ejacula- and masses within the scrotal contents or spermatic
tory dysfunction of medical origin are uncommon. cord. Breeding behaviour is observed including the
stallion’s attitude, number of mounts, position when
Aetiology/pathophysiology mounted, vigour of thrusting and character of ure-
Ejaculatory failure is most frequently caused by sys- thral pulsations. The temperature of the artificial
temic abnormalities that hinder pelvic thrusting. vagina is checked to see if it is in the correct range of
These include arthritis of the spine and hindlimbs, 43–48°C (109.4–118.4°F). Emitted fluid is examined
neurological disease and aortoiliac thrombosis. for the presence of spermatozoa or spermatazoal