Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

Clinical Examination of the Male Genital System
the bull makes thrusting movements with his
penis and back. These may be progressively
more intense until the final thrust. At this point
the bull usually jumps. His hind legs briefly leave
the floor, allowing the penis to reach the anterior
fornix of the cow and triggering the ejaculation
reflex.
(5) Dismounting The bull usually dismounts immediately
after ejaculating, sliding backwards and
sideways off the cow to take his weight on his
four legs.
(6) Penile retraction Contraction of the retractor penis
muscle should normally result in rapid retraction
of the penis back into the prepuce.
Observation of mating should reveal any abnormalities
in service behaviour and ability. If libido is good,
a further service may be observed to see if the abnormality
noted is a feature of each service. If equipment
is available, service can be recorded on video for
further viewing and analysis.
Specific abnormalities
Specific abnormalities which may be confirmed and
elucidated by observation and enquiry are described
below with the most important causes of each
problem.
Deficient libido Immaturity, old age, systemic disease,
fear and other psychological factors.
Inability to mount Orthopaedic abnormalities of
the feet, legs and back. Neurological injuries or
deficits. Unsuitable floor or ground surfaces.
Inability to achieve intromission Disparity in body
size between male and female. Inability to extrude
the penis (phimosis), persistent frenulum, spiral deviation
of the penis. Inability to fully erect the penis
(anastomoses between arterial and venous blood
vessels interfering with the normal erectile mechanism).
Adhesions between the penis and prepuce, for
example in rupture of the tunica albuginea of the
penis (‘fractured penis’). Neoplasia, for example
very large fibropapillomata arising from the glans
penis. Smaller fibropapillomata may not prevent
penile movements but may cause exposure of the
spermatozoa to blood arising from minor trauma
and adversely affect fertility. Failure of the retractor
penis muscle to relax may also prevent extrusion of
the penis.
Inability to fertilise This may occur if sperm production
is reduced or absent through injury to or infection
of the testes and other organs of reproduction.
Genetic and immunological factors can also reduce
sperm production. Transmission of venereal diseases,
such as campylobacteriosis and trichomoniasis,
may also have an adverse effect on fertility of the
bull or the cows he serves.
(4) Collection of semen from the bull
Semen is normally collected using an artificial vagina
in the presence of a cow in oestrus. Semen can also be
collected by electroejaculation and in some cases by
massage of the intrapelvic urethra and accessory sex
glands.
Collection of semen using an artificial vagina
The construction of the artificial vagina (AV) is
shown in (Fig. 11.9). The AV is carefully prepared before
use and the cow is secured ready for collection.
The AV is filled with warm water at a temperature of
40°C. The caudal part of the AV is lubricated with an
inert jelly. The clinician, who should wear a hard helmet,
stands close to the bull ready to place the AV in
position as he mounts the cow. If the clinician is too
close there is a possibility that a nervous bull may be
inhibited from serving. If too far away the clinician
cannot reach the bull before he achieves intromission
and serves the cow before the AV can be correctly
positioned.
As the bull mounts the cow, the clinician grasps the
prepuce to deviate the penis laterally towards the AV.
The AV is placed over the tip of the glans penis and
moved back towards the prepuce. This movement
normally stimulates the final thrust and ejaculation,
and the bull dismounts. As the bull dismounts the
caudal part of the AV is raised to allow the semen to
pass into the collecting vessel at the cranial end of
the AV.
Most bulls serve quite readily into the AV. If the
bull is reluctant to serve, the temperature and
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