Clinical Findings
Behavioral aberrations range from frequent,
intermittent estrus with exaggerated monosexual drive to bull-like
behavior (bulling), including mounting, pawing the ground, and
bellowing. This behavior may be accompanied by masculinization of the
head and neck. Relaxation of the vulva, perineum, and the large pelvic
ligaments, which causes the tail head to be elevated, can occur in
chronic cases. Some affected cows show these signs, but others may be
sexually quiescent; anestrous cows are the most common presentation.
This variation is due to the duration of the condition and the nature of
the hormone signals or lack thereof from the diseased ovary.
The affected ovaries generally are enlarged and
rounded, but their size varies, depending on the number and size of
cysts. Their surface is smooth, elevated, and blister-like, particularly
when cysts exceed 2.5–3 cm in diameter. Cysts frequently are multiple
and may approach 4–6 cm in diameter.
Under the influence of hormones
produced by the cystic ovary or the lack of hormones (especially
progesterone) normally present during estrous cycles, the uterus
undergoes palpable changes, which in turn vary with the duration of the
cystic condition. Thus, during the first week, the uterine wall is
thickened and edematous as an extension of the preceding estrus. Toward
the end of the first week, the uterine wall develops a sponge-like
consistency. In chronic cases, atony and atrophy of the uterine wall are
common. Occasionally, the uterine horns become markedly shortened. Some
degree of mucoid to mucopurulent vaginal discharge is common.
Hydrometra, a fluid-filled, extremely thin-walled uterus, is seen
occasionally.
Diagnosis
Palpation of the uterus is helpful to differentiate a
follicular cyst from a dominant preovulatory follicle; only the estrous
cow has a coiled, extremely turgid uterus and a follicle. As noted
earlier, cystic cows fail to ovulate a preovulatory follicle after
undergoing CL regression and, on examination of the reproductive tract,
they present with a large follicle, absence of a CL, and absence of a
turgid uterus. Ultrasound technology per rectum can be used to
differentiate cysts from corpora lutea and may be helpful in diagnosing
cyst type (ie, follicular vs luteal). Larger, multiple cysts are easily
identified by rectal palpation. History, conformation, and uterine
changes, when present, provide supplemental diagnostic evidence.
Treatment
The disease responds readily to an LH-type hormonal
treatment. In the past, human chorionic gonadotropin (hCG) was commonly
used. It is most effective at 10,000 USP units IM, although success with
lower doses given IM or IV has also been reported.
Hormone therapy with GnRH is effective at 100 μg and
less antigenic than hCG. To hasten the onset of the first estrus after
treatment, prostaglandin (PG) F2α products can be given 7 days after hCG or GnRH. Ovulation synchronization protocols, such as OvSynch, combine GnRH and PGF2α
to control follicular dynamics, luteolysis, and ovulation. They allow
for fixed timed artificial insemination (TAI) of cattle without the need
for estrus detection, and have been successfully used to treat cows
with cystic ovaries. This protocol consists of giving GnRH, then PG 7
days later, then a second administration of GnRH 48 hr later, and
finally TAI 0–24 hr later. The claim that breeding on the first estrus
is prone to produce twins has not been substantiated. In fact, breeding
on the first estrus reduces danger of recurrence by establishing
pregnancy as soon as possible.
The potential danger of traumatizing the ovary and
causing hemorrhage with subsequent local adhesions should not be
overlooked, but manual rupture has been used often without problems.
This method should be weighed against the cost of hormone therapy.