Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

Clinical Examination of the Female Genital System
Mature follicle Corpus albicans Corpus luteum
Left ovary
Right ovary
Figure 10.7 Diagrammatic representation of a cycling cow.The cow has a
mature follicle on her left ovary and the regressing corpus luteum from the
previous cycle on her right ovary.A corpus albicans from an earlier pregnancy
is still palpable on the left ovary.
The ovaries are firmer than adjacent tissues and
one, currently the more active ovary, is larger than
the other. Inactive ovaries in postpubertal cattle are 1
to 1.5 cm at their largest diameter. Active ovaries are
usually 2.5 to 3.0 cm in diameter, but are occasionally
larger. Ovarian shape is very variable and is influenced
by the ovary’s physiological activity and the
presence of follicles and corpora lutea. Cystic ovaries
may be considerably enlarged and are discussed
below.
Once located, the ovaries should be palpated in detail.
They can be picked up by the clinician using the
thumb and second finger. The surface of the ovary is
palpated with the first finger (Fig. 10.7). As much of
the ovarian surface as possible is explored, testing for
shape and consistency. Ovarian follicles are fluid filled
and readily compressible, with a smooth surface
often rising just above the ovarian surface. More than
one follicle may be present, but as oestrus approaches
a single follicle may become dominant and grow
faster than the others. Mature ovarian follicles are up
to 2 cm in diameter. Just before ovulation the ripening
follicle may soften. Immediately after ovulation a
small depression may be palpated at the site of ovulation.
This is later palpable as the spongy corpus
rubrum which later becomes luteinised as the corpus
luteum. Corpora lutea project from the ovarian surface
and are firm and non-compressible to the touch
(Fig. 10.7). The young corpus luteum is slightly compressible.
It hardens with age and sinks back into the
ovarian stroma but may still be palpable as a small
corpus albicans after it ceases to be active. During
pregnancy the ovaries are palpable until about 90
days after conception. After that they are pulled forward
beyond reach by the enlarging uterus.
Both ovaries must be examined before the clinician
can evaluate their activity and identify the stage of
the patient’s oestrous cycle. Evidence of previous
cyclical activity is often present. Ovulation may
occur sequentially on the same ovary or alternate
between the two ovaries. The absence of follicles or
corpora lutea may suggest that the patient is in
anoestrus. A further rectal examination should be
made 10 to 14 days later to confirm or refute the absence
of cyclical ovarian activity. Further evaluation
of the ovaries by ultrasonography and a plasma or
milk progesterone profile of the patient are extremely
useful in confirming the physiological state of
the ovaries. These techniques are discussed in
greater detail below.
Cystic ovarian disease Ovarian cysts are very common
in dairy cattle and can be readily diagnosed on
rectal examination. In most cases a single ovary is
involved, but occasionally bilateral cysts are seen.
Cysts are defined as being fluid filled structures
greater than 2.5 cm in diameter. Ovaries containing
cysts may be grossly enlarged and their overall diameter
may occasionally exceed 5 to 6 cm. Ovarian cysts
are broadly classified into two main groups whose
clinical and diagnostic features are summarised
below.
Follicular cysts – may be associated with short oestrous
cycles, irregular oestrus and nymphomania.
Cysts are normally thin walled (3 mm); progesterone is secreted.
Granulosa cell tumours These large irregular tumours
are uncommon in cattle. They usually involve
one ovary which is grossly enlarged, has a variable
hormone secretion and may hang over the pelvic
brim.
135