Confusion Concerning the Diagnosis, Cause, and Treatment of Cystic Ovarian Disorders
Posted: April 20, 2009
The incidence of cystic ovarian disorders within a lactation has been estimated average 10% with a range among studies between 6 and 23%. There have been several definitions of cystic ovarian disorders. The majority of ovarian cysts are follicular with a smaller percentage being luteal cysts. Originally follicular cysts were defined as follicular structures over 2.5 cm in diameter that persisted for various periods of time without the presence of a corpus luteum (CL). Currently experts define the a follicular cysts as a follicle greater than 17mm usually accompanied by one or more other large follicular structures and no CL present. To further complicate this syndrome is the fact that most follicular cysts are dynamic in that they disappear and are replaced by new cysts or simply disappear with the onset of normal cycles. A smaller percentage of follicular cysts persists and are classified as chronic cysts. Thus accurate diagnosis of cystic ovaries can be a difficult task and is a major challenge to veterinarians. Each type of cyst (follicular or luteal) requires a specific hormonal treatment. Studies using either progesterone analysis, ultrasound monitoring of ovarian structures or both methods have consistently shown a significant error rate in distinguishing between follicular and luteal cysts based palpation of the ovaries. Research from North Carolina State University determined that the overall correct diagnosis of the type of cyst was 51% with palpation and 85% using ultrasound. The investigators noted these differences were probably due to the more accurate detection of luteal tissue within the ovary using ultrasonography. Unlike the chronically cystic cows 30 years ago which were in constant or frequent estrus, research data indicates that about 80% of the cows with a cystic disorder are anestrus - fail to exhibit estrus. There are several theories that attempt to explain the physiological mechanisms responsible for the development of cysts. It is a complex problem. From a management standpoint we must look for health, genetic, or management factors associated with a higher than average incidence of cystic ovaries in some herds.
This condition is most common during the first 60 days of lactation when cows experience the most health disorders and are under metabolic stress. Several surveys indicate that cows experiencing problems around the time of calving were most likely to develop ovarian dysfunction. These problems include twinning, dystocia, retained placenta and uterine infection. The condition is more common is second and greater lactation cows than younger cows. This is interesting in that older cows experience a higher rate of periparturient problems. Metabolic disturbances due to severe negative energy balance or ketosis were also related to development of cysts. More recently it has been shown that cows over conditioned at dry off were 2.5 times more likely to develop cystic ovaries after calving than herdmates in average condition. Since most cysts develop in early lactation people thought that high production was the major cause of the problem. More recently it has been shown that cows either produce an equal amount or more milk when they are cystic. There is not much direct evidence of a major genetic component to this condition.
As noted above, each type of cyst, follicular and luteal, requires different hormonal treatments. Traditionally gonadotropic releasing hormone (GnRH) or a lutenizing hormone-like product were used to treat follicular cysts and prostaglandin (PG) products were effective for luteal cysts. Since the standard Ovsynch timed- insemination protocol utilizes both GnRH and PG, this program has been used routinely to treat cystic ovarian conditions. Recently the use of progesterone implants (CIDR) along with a PG injection has also been shown to be effective. The question is frequently asked which treatment is most cost effective. A comprehensive study conducted in Florida using 400 cows diagnosed with cystic ovaries compared treatment of cystic ovaries using progesterone treatment (CIDR) with a PG injection given on day 7 when the CIDR is withdrawn to the standard Ovsynch timed – insemination program protocol. Cows on the CIDR / PG treatment were watched for estrus and those identified in heat were inseminated. The Ovsynch cows were time inseminated without heat detection.
The percentage cows inseminated using the Ovsynch and CIDR/PG programs were 82% and 44%, respectively. Conception rate (% conceived of those inseminated) and pregnancy rate (% of the total cystic cows in the group that conceived) for cows in the CIDR group were 23% and 9.5%, respectively. Conception rate and pregnancy rate for the cystic cows on the Ovsynch program were 18.3% and 14 %, respectively. There were no statistically significant differences between treatments. However, the cost effectiveness of the treatments must be considered. As a follow-up to that study a complex economic analysis (DeVries et al. 2005, Journal of Dairy Science) was conducted using success rates and the costs of treatment. The overall results were that the Ovsynch with timed AI protocol for cystic cows provided an $11.39 greater economic advantage per cow than the CIDR/ PG / heat detection system (assumed 46% probability of heat detection). If the heat detection rate following the CIDR/PG program improved to 70% the benefit of the CIDR / PG program improved but was still less than the standard Ovsynch timed AI program.
Progress is be made to understand more about this condition and treatment strategies have improved but diagnosis of the type of cysts is still a challenge. However, culling chronically cystic cows, developing a strategy to avoid over conditioned dry cows and providing balanced transition cow ration will certainly help minimize periparturient problems so that the incidence of cystic ovaries remains low.Michael O'Connor, Dairy and Animal Science Extension