Kvet Forum
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The incidence of cystic ovarian disease (COD) varies between 5% and 30%, with most cases developing 20–60 days post partum and affecting second and third lactation, high-yielding dairy cows. The disease is rarer in beef cows.
Aetiology
Follicular cysts develop due to either failure of the LH surge around the time of normal ovulation or failure of the follicle to respond to LH. The follicle fails to ovulate and, instead of becoming atretic, continues to grow to form a cyst. Cystic follicles initially produce oestradiol, which suppresses further follicular development in the ovaries, and then they enter an oestrogen-inactive phase, which can persist for many weeks. Many cysts that form during the early post-partum period (<30 days) regress spontaneously without treatment. Some follicular cysts become luteinized and persist as luteal cysts.
Clinical Presentation
Follicular Cyst
Luteinized or luteal cysts
An ovarian cyst is defined as a fluid-filled structure >2.5 cm in diameter that is present for more than ten days on one or both ovaries in the absence of a corpus luteum (CL). Cysts can be classified either as follicular cysts, which are thin-walled and non-progesterone producing, or luteinized or luteal cysts, which are thicker walled (>3 mm) and produce progesterone. Many normal CLs have fluid-filled centers (lacunae) visible on ultrasound scan and must not be mistaken for luteal cysts.
Cows with follicular cysts are usually anestrus, but some cows show recurrent and irregular estrous activity (nymphomania). Cows with luteinized cysts are anestrus.
Diagnosis
It is difficult accurately to define the type of cyst by manual rectal palpation. Milk or blood progesterone analysis may increase the accuracy of manual rectal palpation.
Follicular and luteal cysts can be differentiated with reasonable accuracy by transrectal ultrasound examination on the basis of morphology, with cysts showing a wall thickness of >3 mm classified as luteal. If a cyst is detected by ultrasound on one ovary, the other ovary should also be scanned carefully for the possible presence of a CL. Follicular cysts can be found in pregnant cows, reinforcing the fact that cysts can persist as non-functional anatomical structures for weeks or months.
Management of Follicular Cysts
Treatment of ovarian cysts is recommended in cows more than 30 days post partum in order to reduce the potential delay in interval to first service.
Treatment options include:
Management of Luteal Cysts.
Prostaglandin F2α can be administered when confident of the diagnosis of a luteal cyst, with return to estrus expected within 2–5 days.
Overall Management.
At present, the best advice to help reduce the incidence of cystic ovarian disease in dairy cows is to manage them in such a way as to minimize negative energy balance and metabolic and management stress in early lactation, as these factors have been associated with higher incidence of disease.
Cystic ovarian disease causes financial loss associated with a 20–60-day increase in the calving to conception interval.
Aetiology
Follicular cysts develop due to either failure of the LH surge around the time of normal ovulation or failure of the follicle to respond to LH. The follicle fails to ovulate and, instead of becoming atretic, continues to grow to form a cyst. Cystic follicles initially produce oestradiol, which suppresses further follicular development in the ovaries, and then they enter an oestrogen-inactive phase, which can persist for many weeks. Many cysts that form during the early post-partum period (<30 days) regress spontaneously without treatment. Some follicular cysts become luteinized and persist as luteal cysts.
Clinical Presentation
Follicular Cyst
Luteinized or luteal cysts
An ovarian cyst is defined as a fluid-filled structure >2.5 cm in diameter that is present for more than ten days on one or both ovaries in the absence of a corpus luteum (CL). Cysts can be classified either as follicular cysts, which are thin-walled and non-progesterone producing, or luteinized or luteal cysts, which are thicker walled (>3 mm) and produce progesterone. Many normal CLs have fluid-filled centers (lacunae) visible on ultrasound scan and must not be mistaken for luteal cysts.
Cows with follicular cysts are usually anestrus, but some cows show recurrent and irregular estrous activity (nymphomania). Cows with luteinized cysts are anestrus.
Diagnosis
It is difficult accurately to define the type of cyst by manual rectal palpation. Milk or blood progesterone analysis may increase the accuracy of manual rectal palpation.
Follicular and luteal cysts can be differentiated with reasonable accuracy by transrectal ultrasound examination on the basis of morphology, with cysts showing a wall thickness of >3 mm classified as luteal. If a cyst is detected by ultrasound on one ovary, the other ovary should also be scanned carefully for the possible presence of a CL. Follicular cysts can be found in pregnant cows, reinforcing the fact that cysts can persist as non-functional anatomical structures for weeks or months.
Management of Follicular Cysts
Treatment of ovarian cysts is recommended in cows more than 30 days post partum in order to reduce the potential delay in interval to first service.
Treatment options include:
- GnRH analogues.
GnRH induces an LH surge, effecting luteinization (not ovulation) of the follicular cyst and possibly ovulation or luteinization of any mature follicles present in the ovaries. Successful treatment should produce a rise in plasma progesterone concentration to normal luteal phase values within seven days and 80% of cows show estrus within 30 days. PGF2α can be given 7–14 days after GnRH treatment if estrus has not yet occurred. Ultrasound monitoring of GnRH-treated cows will show regression or luteinization of follicular cysts and/or appearance of a CL if treatment has been successful. - Human chorionic gonadotropin (hCG).
Injection of hCG, which is an LH agonist, can be used to treat follicular cysts, with the mode of action as described for GnRH. Return to estrus is variable, but usually within 20–30 days post treatment. - Progesterone treatment - PRID/CIDR.
A PRID or CIDR device is inserted into the vagina for 7–10 days. The mechanism of cure is not clear, but treatment probably causes atresia of the follicular cyst by suppression of LH support through progesterone-negative feedback. Estrus normally occurs within 2–3 days of PRID/CIDR removal, along with ovulation of a new dominant follicle. - Manual rupture of ovarian cysts is not recommended because of possible trauma/haemorrhage within the ovary and its bursa.
Management of Luteal Cysts.
Prostaglandin F2α can be administered when confident of the diagnosis of a luteal cyst, with return to estrus expected within 2–5 days.
Overall Management.
At present, the best advice to help reduce the incidence of cystic ovarian disease in dairy cows is to manage them in such a way as to minimize negative energy balance and metabolic and management stress in early lactation, as these factors have been associated with higher incidence of disease.
Cystic ovarian disease causes financial loss associated with a 20–60-day increase in the calving to conception interval.