Defining uterine disease in dairy cows
Dr. Adrian Barragan, Penn State Extension veterinarian, said uterine diseases are among the most problematic diseases in dairy cows. Uterine diseases can cost both time and money, and there’s also potential for losing valuable genetics due to culling.
While costs vary from herd to herd, uterine disease typically costs between $100 and $400 per case. Barragan said that’s the direct cost for veterinary treatment and drug expenses, but there are also indirect costs through poor reproductive performance or low milk production. “If we consider that over the entire lactation, it becomes a significant cost,” he said. “Culling rate is high. Not only is performance impaired, it’s also a welfare issue – animals with uterine disease have higher biomarkers for inflammation, stress and pain.”
Definitions are important for accurate identification and disease monitoring. To develop solid protocols for identifying and treating uterine disease, all farmworkers should understand agreed-upon definitions for uterine diseases. Barragan encouraged farm managers to work with the herd vet to include definitions in treatment protocols.
“Retained placenta [RP] is the easiest to define and diagnose,” said Barragan. “It’s the failed expulsion of the placenta within 24 hours after calving. Another accepted definition is within the first 48 hours after calving.” The nationwide incidence of RP is about 8.6% but can be higher in poorly managed herds.
Risk factors for RP are related to issues around calving such as dystocia, twins, abortion, induction of calving and, to a lesser degree, hypoglycemia and ketosis. The main losses from RP include increased risk of metabolic disease or clinical disease such as mastitis, metritis or endometritis. Cows often drop in milk production and have poor reproductive performance.
Metritis is infection of the uterus, usually caused by bacteria. It is characterized by an enlarged uterus with an abnormal discharge. Barragan has conducted extensive research on metritis and said the national average for metritis in most herds is 15% – 20% but can be as high as 40% – 50%.
A cow with localized metritis has an enlarged uterus and watery, reddish-brown discharge. In some cases, metritis advances to a systemic condition with fever, depression, anorexia and drop in milk. Metritis can be defined as one disease or two, depending on farm definitions and protocols. “In my experience, the cows being scored and treated are the ones with systemic signs,” he said.
Barragan explained the use of metritis scoring to determine the severity of the condition. A cow with clear discharge has a score of 1; a score of 2 is a discharge with flakes of pus, less than 50% pus and resolves on its own; a score of 3 is more than 50% purulent discharge (mostly pus) and usually resolves on its own; cows with a score of 4 or 5 have a reddish-brown, smelly discharge. “The 4s and 5s have more severe clinical metritis and have fever,” said Barragan. “Only 11% of animals diagnosed would be severe metritis.”
Risk factors for metritis are similar to RP, including dystocia, twins, hypoglycemia and ketosis. The main losses are due to drop in milk yield, poor reproductive performance and higher risk of leaving the herd.
Endometritis occurs 21 days post-calving and is a milder condition that affects only the endometrium – the first layer of the uterus. “It causes a purulent vaginal discharge,” said Barragan. “It can be classified as clinical with purulent vaginal discharge or subclinical with no visible signs.” Testing helps to determine the concentration of neutrophils, a form of white blood cell, in the endometrium.
The incidence of endometritis ranges from 10% – 50%. Barragan said the range is due to the more prevalent clinical form. In general, it’s a milder condition that doesn’t have a systemic form but it can affect reproductive performance and result in failure to conceive.
Pyometra, which Barragan said is a less prevalent uterine disease, is the accumulation of purulent fluid in the uterus. “With the presence of a CL (corpus luteum, formed when ovulation results in pregnancy), the cervix is usually closed,” said Barragan. “The CL keeps the cervix closed and the purulent discharge accumulates in the uterus.” Some farms have high incidence of pyometra, usually associated with management issues in transition cows. “They are not using any synchronization hormones,” he said. “Many of the hormones used to synchronize animals help to open the cervix to expel the abnormal fluid and resolve the condition.”
Because these four uterine diseases usually occur at specific times after calving, developing protocols and diagnostics should begin with establishing a timeframe during which animals will be monitored and assessed for disease.
The first risk of uterine disease is RP and occurs following calving. Metritis can occur up to 21 days in milk, while endometritis occurs at around 21 days in milk, followed by pyometra. Timely, accurate disease identification and detection facilitates prompt treatment and a favorable outcome.
Ideally, protocols involve weekly checks. “For metritis, the best day to do diagnostics is around seven days in milk,” said Barragan. “Check animals that are between four and 10 days in milk to get most of the animals that develop this condition. After 14 days, there aren’t many cases of metritis.”
Some diagnostics can be performed by the herd manager, while other procedures are done by a veterinarian. Metritis occurring early in lactation is more complicated to diagnose because the uterus is very large and ultrasound may not have the capacity to penetrate the tissue for a good assessment of the uterine wall.
“For clinical metritis, we can do the same diagnostics as for metritis, plus use ultrasound because the uterus is much smaller now and easier for ultrasound to assess,” said Barragan. “Clinical metritis requires more specified techniques such as uterine cytology or uterine biopsy. Ultrasound can be used, although it isn’t as accurate. With pyometra, the cervix is closed, so assessing vaginal discharge is not useful. Ultrasound and palpation can aid in pyometra diagnosis.”
One of the most important diagnostic aids is visual observation, which is free and requires little training. “Walk the pen a few hours after milking when cows have eaten and are lying down in stalls,” he said. “Look for the discharge as cows are lying down.” The only issue with observation is false negatives because animals a week or two post-calving have a smaller, tighter cervix and potentially less discharge.
The gold standard for monitoring endometritis is Metricheck, which is used to collect vaginal discharge. Transrectal sonography can determine the thickness of the uterine wall, diameter of the cervix and presence and amount of abnormal fluid in the uterus as well as the structure of the ovaries.
“These are highly prevalent diseases and they cause important losses on the dairy,” said Barragan. “Most importantly, we have to have accurate definitions to develop clear protocols.”
by Sally Colby
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