Follicular Cystic Ovary

The presence of a thin-walled, fluid-filled structure >25 mm diameter and present for >7 days in the absence of cl

Incidence

The incidence of cystic ovarian follicles (COF )is much greater in dairy cows compared with beef cattle and dairy heifers, where the incidence is

relatively low.

Utilizing data from a number of studies, the average incidence of COF in lactating dairy cattle is estimated to be near 10–12%, with various studies reporting incidences ranging from 3 to 32%.

There are numerous factors that can impact the apparent incidence of COF.

Physiology of COF formation

A dysfunction or neuroendocrine imbalance involving the normal hypothalamic–pituitary–gonadal axis resulting in ovulation failure is the basic accepted mechanism of COF formation.

The most widely accepted hypothesis involves the altered release of luteinizing hormone (LH) from the pituitary gland. The preovulatory surge of LH is absent, insufficient in magnitude, or improperly timed leading to failure of the dominant follicle to ovulate. The dominant follicle continues to grow and becomes large and anovulatory.

cows with follicular cysts are often concurrently or were previously exposed to various kinds of insults or stress such as oxidative stress, negative energy balance, reduced or poor liver function, and low circulating insulin-like growth factor (IGF)-1.

Clinical Findings:

Behavioral aberrations range from frequent, intermittent estrus with exaggerated monosexual drive to bull-like behavior, 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 or subestrous cows are a common presentation.

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. 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

Transrectal palpation of the reproductive tract has been the primary means of diagnosing COF for many years. However the accuracy with which one can determine the specific type of cyst present is relatively poor. However, transrectal ultrasound can be very useful in determining the specific type of cyst present.

Follicular cysts typically have a thin wall (≤3 mm) whereas luteal cysts typically have a thicker and more echogenic wall (≥3 mm).

The follicular fluid is often hypoechoic in follicular cysts, whereas with luteal cysts

echogenic strands may be present creating a cobweb-like appearance.

The collective findings of a rectal examination of the reproductive tract including

ultrasonography, blood progesterone levels, and the clinical history of the cow will

allow the most accurate diagnosis regarding the type of cyst present.

The dynamic nature of both cysts and developing corpora lutea can complicate the diagnosis when palpation alone is used.

Farin et al.  showed that 10%of cows diagnosed as having cysts based on rectal examination were found to have a structure consistent with a normal CL when the ovaries were subsequently examined with ultrasound

When ultrasound technology was used the accuracy of a correct diagnosis of cyst type was 74% for follicular cysts and almost 90% for luteal cysts

when blood progesterone concentration is combined with both palpation and ultrasound findings, the diagnosis of cyst type approaches 100%

Treatment:

Hormone therapy with GnRH (Receptal)may be effective 

100 mcg and less antigenic than hCG.

To hasten the onset of the first estrus after treatment, 

prostaglandin (PG) F_2α products can be given 7 days aftrer 

hCG or GnRH.