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Endometritis refers to inflammation of the uterine lining, or endometrium. Cows with endometritis are significantly less likely to get pregnant in a timely manner, and are more likely to get culled (Giuliodori 2011). Technically, the diagnosis is made by microscopic examination of endometrial biopsy specimens. This is not practical in the field, so in cows, we typically define clinical endometritis as presence of a purulent discharge detectable in the vagina after 26 days postpartum. Subclinical endometritis is defined by the presence of polymorphonuclear neutrophils (a type of white blood cell) greater than 5-10 percent of cells in samples collected from the uterine lumen. Endometritis is not the same as metritis. The term metritis refers to cows, usually within days or a few weeks of calving, with a purulent uterine discharge and an enlarged uterus. Cows with metritis may be systemically ill.
To confuse things a bit further, it turns out that presence of a purulent discharge in the vagina does not necessarily mean that there is inflammation of the uterine lining as determined by microscopic examination. A recent study determined that at least 37 percent of cows with pus in the vagina did not have microscopic evidence of endometritis. (Peter 2011). Surprisingly though, cows with vaginal pus but with no microscopic signs of endometritis still have impaired fertility. So it appears there may actually be three different conditions: purulent vaginal discharge, vaginal discharge with endometritis, and endometritis without vaginal discharge. Putting them all together, we find that a substantial proportion of dairy cows are affected. Studies in Canada and the northeastern US have found prevalence of 37 to 74 percent when cows were examined between 34 and 60 days postpartum. Thus, we have a disease, or a group of diseases, that cause significant reproductive losses in dairy herds today.
Competent veterinarians and dairy managers should simply identify affected animals, treat them appropriately and see reproductive performance improve, no?
Unfortunately, it is not that easy. For one, the disease is difficult to diagnose. Clinical endometritis can be diagnosed by using a vaginoscope, or by inserting a gloved arm through the vagina to the level of the external os of the cervix and then examining the fingers upon removal for evidence of pus. There is also a device designed for this purpose called a Metricheck, which is inserted into the vagina and used to collect samples of vaginal discharge for visual examination. The Metricheck is commonly used in New Zealand where seasonally dairying makes a short interval from calving to conception imperative for success. Cloudy fluid within the uterus seen with ultrasound is another method of diagnosis. However, diagnosis can be difficult. Indeed, most of these methods may fail to find 40 to 65 percent of cows with endometritis.
Assuming we can correctly diagnose cows with endometritis, how can we treat them to improve reproductive outcomes? There are a variety of studies that have looked at this. An often quoted study from New Zealand showed a significant improvement in reproductive performance when cows diagnosed positive via Metricheck were treated with intrauterine cephapirin. There is a cephapirin product approved for this use in New Zealand and other countries. Other studies have found positive effects from administration of prostaglandins if a corpus luteum is present on either ovary. However, different studies have shown no effect of intrauterine antibiotics or prostaglandin. This may be due to the fact that bacteria are often not isolated from subclinical endometritis, or because many cows with endometritis do not have observable corpora lutea, which are required for prostaglandins to work.
We seem to be stuck with a disease that has pretty high prevalence, has significant negative effects on reproduction, is difficult to correctly diagnose and often difficult to correct via treatment. Like so many diseases, prevention is thus critical.
Metritis and other postpartum diseases have been shown to be directly linked to dry matter intake in the prepartum cow. Cows with metritis are twice as likely to develop endometritis. Thin cows and cows with subclinical or clinical ketosis post calving are also at risk for endometritis. Cows with elevated haptoglobin, an indicator of inflammation, before and after calving are at greater risk for endometritis. There seems to be consensus that these diseases really are the result of inflammation and impaired immune function that occur due to negative energy balance. It is likely that endometritis is a result of impaired immune function that is often secondary to negative energy balance. Prevention, then, is all about maximizing dry matter intake in prefresh and post fresh cows. Ovarian function is also commonly reduced by postpartum infection. Reduced ovarian function is another significant cause of infertility in early lactation cows. Clearly then, negative energy balance is a major contributor to impaired reproduction on many dairy farms.
Still confused? I am. However, it is clear that minimizing negative energy balance pre and post partum is critical for maximum cow health and fertility. Everyone can work on that. It is also clear that endometritis is a significant problem on many farms, and that there are several methods to diagnose it with reasonable sensitivity and specificity. While successful treatment of individual animals may be difficult, hopefully, over time, better definitions and treatments will be developed. Until then, diagnosis is still important because we can identify the problem and work toward solutions by improving management of pre and post fresh cows.[[In-content Ad]]

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