Endometritis

Endometritis is a localized inflammatory condition of the uterine lining that represents one of the most economically significant reproductive disorders in dairy cattle and other livestock species. Unlike the more severe systemic condition of metritis, endometritis is characterized by inflammation confined to the endometrium without systemic signs of illness, though it significantly impairs fertility and extends the interval from calving to conception. This condition affects a substantial proportion of dairy cows in the postpartum period, with studies reporting prevalence rates ranging from 15 to 40 percent depending on the diagnostic criteria used and the population studied.

Endometritis occurs in cattle, sheep, goats, pigs, and horses, though it is most thoroughly studied and economically important in dairy cattle due to the intensive reproductive management required for profitable milk production. The condition typically develops following calving as a continuation of the normal postpartum uterine contamination that all animals experience, but in affected individuals, the uterus fails to clear the infection and return to normal within the expected timeframe. The transition from normal postpartum involution to pathological endometritis represents a failure of the uterine immune defenses to eliminate bacterial contamination.

The economic impact of endometritis in dairy operations is substantial and multifaceted. Affected cows have reduced conception rates, requiring more inseminations to achieve pregnancy and extending the calving interval. The extended days open result in lost milk production over the lifetime of the cow, as she spends more time in late lactation when production is naturally lower. Treatment costs, veterinary fees, and the labor involved in identifying and managing affected cows add to the economic burden. Cows that fail to conceive despite treatment face early culling, representing loss of genetic potential and replacement costs.

Endometritis is a treatable condition with several effective therapeutic options available, and most affected cows can be successfully bred following appropriate treatment. However, treatment success depends on accurate diagnosis, appropriate therapy selection, and adequate time for uterine healing before breeding. Prevention through management of the transition period, reduction of calving complications, and optimization of immune function reduces endometritis incidence and associated losses. Understanding the relationship between endometritis, other postpartum diseases, and fertility is essential for effective reproductive management in dairy herds.

Endometritis results from bacterial infection of the uterine lining, typically developing as a progression from the normal postpartum bacterial contamination that occurs in virtually all animals following parturition. The bacteria most commonly isolated from endometritis cases include Trueperella pyogenes, Escherichia coli, Fusobacterium necrophorum, Prevotella melaninogenica, and various other opportunistic organisms. These bacteria enter the uterus during and after calving from the environment, the animal's own fecal flora, or contamination during assisted deliveries. In healthy animals, the uterine immune system eliminates these bacteria within two to three weeks, but in animals that develop endometritis, the infection persists.

While endometritis itself is not hereditary, genetic factors influence susceptibility through effects on immune function, uterine physiology, and other predisposing traits. Studies have identified genetic variation in the immune response to uterine infection, with some individuals mounting more effective bacterial clearance than others. Heritability estimates for endometritis and related postpartum disorders suggest modest genetic influence. Selection for improved fertility and disease resistance may reduce endometritis susceptibility over generations, though environmental and management factors remain the primary determinants of disease occurrence.

Environmental and management factors are the most important determinants of endometritis risk. Calving conditions have profound effects, with dirty or contaminated calving areas increasing bacterial exposure. Assisted deliveries, particularly those involving intrauterine manipulation, introduce bacteria and cause tissue trauma that impairs immune function. Retained placenta dramatically increases endometritis risk by providing a medium for bacterial growth and preventing normal uterine involution. Nutritional status during the transition period affects immune function, with negative energy balance and metabolic disorders compromising the cow's ability to clear uterine infection.

Specific risk factors for endometritis development include dystocia, retained placenta, twins, stillbirth, metabolic disorders such as hypocalcemia and ketosis, and previous reproductive tract infections. Cows experiencing any of these conditions at or following calving should be considered at elevated risk for endometritis and monitored accordingly. Body condition loss during the dry period and early lactation indicates negative energy balance that impairs immune function. Older cows and those with previous endometritis history have increased risk compared to young, healthy animals with uncomplicated calvings.

The pathophysiology of endometritis involves failure of the normal uterine defense mechanisms to eliminate postpartum bacterial contamination. Following calving, the uterus is contaminated by bacteria from the environment and the cow's own flora. Normally, physical mechanisms including uterine contractions and fluid drainage, along with immune defenses including neutrophil influx, antimicrobial peptide production, and acquired immune responses, eliminate bacteria and restore a sterile uterine environment within approximately three weeks. In endometritis, these mechanisms are overwhelmed by bacterial load, compromised by tissue damage, or impaired by systemic factors such as negative energy balance, allowing persistent infection that damages the endometrium and impairs fertility.

Early warning signs of endometritis may be subtle and difficult to detect without deliberate examination of postpartum cows. Unlike acute puerperal metritis, which causes obvious systemic illness in the first two weeks after calving, endometritis develops later and does not typically cause fever, depression, or other signs of systemic disease. The primary indicator is abnormal uterine discharge persisting beyond the expected period of normal postpartum lochia. Cows may show subtle signs such as decreased appetite, reduced milk production, or mild discomfort, but many affected cows appear completely healthy on casual observation.

The defining symptom of clinical endometritis is purulent or mucopurulent discharge from the vagina more than three weeks after calving. This discharge may be visible on the tail, perineum, or vulvar lips, or may only be detected through vaginal examination. The character of the discharge provides information about severity, with worse cases showing more purulent, foul-smelling material and milder cases showing only mucopurulent or cloudy discharge. The presence of pus indicates active bacterial infection and inflammatory response. Subclinical endometritis, which affects fertility without producing visible discharge, can only be detected through cytological examination of uterine contents.

Behavioral changes associated with endometritis are often minimal or absent because the infection remains localized to the uterus without systemic effects. Some affected cows may show signs of discomfort when examined rectally or vaginally. Tail switching, frequent urination attempts, or posturing as if to urinate may indicate reproductive tract discomfort. More notably, endometritis affects reproductive behavior, with affected cows often showing irregular estrous cycles, failure to display estrus, or failure to conceive when bred. These reproductive behavioral changes are often the most noticeable indicator of a problem.

Physical examination findings in endometritis center on the reproductive tract. Transrectal palpation may reveal an enlarged uterus that has not involuted normally, with thickened walls and fluid content. The cervix may be open, allowing discharge to drain, or closed, causing fluid accumulation. Vaginal examination using a speculum or vaginoscopy reveals the presence and character of discharge within the vagina and at the external cervical os. Transrectal ultrasonography provides detailed evaluation of uterine contents, wall thickness, and the presence of fluid accumulation. The ovaries should be evaluated for cyclicity, as anovulation commonly accompanies endometritis.

The progression of endometritis symptoms depends on whether the condition resolves spontaneously or persists. Some cases of endometritis resolve without treatment as the uterus eventually clears the infection, though fertility may still be impaired. Persistent cases continue to show abnormal discharge and fail to conceive when bred. Chronic endometritis may develop, with ongoing low-grade infection and permanent changes to the endometrium that severely impair fertility. In some cases, endometritis may progress to pyometra, with accumulation of purulent material in the uterus behind a closed cervix.

Emergency symptoms are not typical of endometritis, as this is a chronic, localized condition rather than an acute systemic illness. However, veterinary attention should be sought for any cow with abnormal vaginal discharge persisting beyond three to four weeks after calving. Cows that develop systemic signs including fever, depression, decreased appetite, or reduced milk production may have progressed to more severe metritis or developed complications such as peritonitis, requiring urgent evaluation and treatment. Any cow that fails to conceive after multiple breedings should be examined for endometritis even if obvious discharge is not present.

Clinical examination for endometritis focuses on the reproductive tract, with transrectal palpation and vaginal examination forming the foundation of diagnosis. History should include calving date, any calving complications, previous postpartum treatments, estrous cycle observations, and breeding history. Transrectal palpation evaluates uterine size, symmetry, tone, and contents, comparing findings to expected normal involution for days postpartum. A uterus that remains enlarged, fluid-filled, or lacks tone beyond expected timelines suggests endometritis. Ovarian structures are assessed to determine if the cow is cycling normally.

Vaginal examination techniques provide critical diagnostic information about discharge character. The Metricheck device, a rod with a cup-shaped end, is inserted into the vagina to collect discharge for visual evaluation. Alternatively, vaginoscopy using a speculum allows direct visualization of the vaginal walls and external cervical os. Discharge is graded on appearance, with clear or cloudy mucus being normal, mucopurulent discharge indicating mild to moderate endometritis, and purulent or foul-smelling discharge indicating severe endometritis. The timing of examination relative to calving is important, as some discharge is normal in early postpartum cows.

Differential diagnosis for endometritis includes normal postpartum involution, which involves some discharge for the first two to three weeks after calving. Pyometra, accumulation of pus in the uterus with a persistent corpus luteum, presents differently with a distended uterus and anestrus. Vaginitis or cervicitis may cause discharge without uterine involvement. Reproductive tumors are rare but should be considered in older cows with persistent abnormalities. Subclinical endometritis, which impairs fertility without producing visible discharge, requires cytological diagnosis and is important in cows that fail to conceive despite appearing normal.

Diagnostic criteria for endometritis have been defined to standardize research and clinical diagnosis. Clinical endometritis is typically defined as the presence of purulent or mucopurulent discharge in the vagina 21 or more days postpartum, or mucopurulent discharge at 26 or more days, without systemic signs of illness. Subclinical endometritis is defined by elevated neutrophil percentage on uterine cytology, typically greater than 5 to 18 percent depending on days postpartum, in cows without clinical discharge. These definitions allow for consistent diagnosis and comparison across studies and herds. Practical clinical diagnosis may be less rigorous but should follow similar principles of evaluating discharge character and timing.

Initial treatment for endometritis aims to eliminate bacterial infection and restore normal uterine function to enable fertility. Treatment approaches include intrauterine antibiotics, systemic antibiotics, hormonal therapy to induce estrus and uterine clearance, and combinations of these methods. The optimal treatment depends on the severity of endometritis, timing relative to intended breeding, and available products and resources. Treatment should be initiated promptly once diagnosis is made to maximize the time available for uterine healing before breeding.

Intrauterine antibiotic therapy delivers antimicrobial agents directly to the site of infection. Cephapirin is the most commonly used product in the United States, formulated specifically for intrauterine use in cattle with established withdrawal times. Intrauterine infusion provides high local antibiotic concentrations at the infection site. Treatment typically consists of one or two infusions. The effectiveness of intrauterine antibiotics depends on adequate distribution throughout the uterus and activity against the bacteria present. Treatment during estrus when the cervix is open may improve distribution and clearance of infected material.

Systemic antibiotic therapy using injectable antibiotics provides an alternative approach that avoids intrauterine manipulation. Ceftiofur, administered systemically, achieves therapeutic concentrations in uterine tissues and has demonstrated efficacy against endometritis pathogens. Systemic therapy may be preferred when intrauterine infusion is not practical or when broader antimicrobial coverage is desired. However, systemic antibiotics for endometritis treatment requires attention to withdrawal periods for milk and meat. The choice between intrauterine and systemic antibiotics may depend on product availability, cost, and practitioner preference.

Hormonal therapy using prostaglandin F2alpha induces luteolysis and estrus in cows with a corpus luteum, promoting uterine contractions, cervical dilation, and clearance of infected material. This approach is particularly useful for cows with endometritis that are cycling but not clearing infection spontaneously. Prostaglandin treatment is often combined with intrauterine antibiotics, with prostaglandin administered to induce estrus followed by antibiotic infusion during the estrus period. For cows that are not cycling, progesterone supplementation followed by prostaglandin may be used to induce cyclicity and provide an opportunity for uterine clearance.

Supportive care and management during endometritis treatment include ensuring adequate nutrition to support immune function and recovery. Negative energy balance impairs uterine immune function, so optimizing energy intake through diet adjustments supports healing. Body condition should be monitored and managed to prevent excessive loss. Concurrent diseases such as ketosis, hypocalcemia, or mastitis should be addressed, as these conditions impair overall immune function and recovery from endometritis.

Treatment decisions for endometritis should balance the costs of treatment against the losses from delayed breeding and reduced fertility. Mild cases may resolve spontaneously, and watchful waiting with reexamination may be appropriate for some cows. Moderate to severe cases benefit from active treatment to accelerate resolution. The timing of breeding following treatment should allow adequate time for uterine healing, typically waiting until normal discharge is present and at least one complete estrous cycle has occurred following treatment. Cows that fail to respond to treatment or have recurrent endometritis may be candidates for culling if reproductive failure persists.

Recovery from endometritis following successful treatment typically occurs over one to three estrous cycles as the uterine lining heals and normal function is restored. Resolution of abnormal discharge is the primary indicator of clinical recovery, with the transition from purulent to mucopurulent to clear mucus indicating improvement. Complete resolution should be confirmed before breeding is attempted, as breeding cows with persistent infection results in poor conception rates and potential ascending infection. Follow-up examination two to three weeks after treatment assesses response and determines if additional treatment is needed.

Post-treatment care focuses on supporting uterine healing and monitoring for resolution. Maintaining adequate nutrition supports immune function and tissue repair. Avoiding additional uterine contamination through unnecessary examinations reduces the risk of recontamination. Monitoring for return of normal estrous behavior indicates that ovarian function has resumed. Record keeping tracks treatment dates and responses to guide breeding timing and identify cows requiring additional intervention.

Prognosis for fertility following endometritis treatment is generally favorable for mild to moderate cases that respond to treatment. Studies show that conception rates in treated cows approach those of unaffected herdmates after successful treatment, though first service conception rates may be somewhat reduced. Cows with severe or chronic endometritis have poorer prognosis, with some experiencing permanent endometrial damage that impairs fertility despite treatment. Early detection and treatment improve prognosis compared to cases where infection persists for extended periods before diagnosis.

Return to breeding following endometritis requires confirmation of resolution and adequate healing time. A minimum voluntary waiting period of 50 to 60 days postpartum is typical for dairy cows, though cows recovering from endometritis may benefit from extended waiting periods. Breeding should only be attempted when normal clear or slight cloudy mucus is observed, uterine involution is complete on examination, and the cow is displaying normal estrous behavior. Pregnancy rates are optimized when these criteria are met, while breeding cows with persistent abnormalities results in poor conception and potential embryonic loss.

Vaccination against specific endometritis pathogens is not currently available or widely used, as the condition results from opportunistic infection by multiple bacterial species rather than a single pathogen. Research into vaccines targeting key endometritis bacteria continues, but practical prevention relies on management strategies rather than vaccination. General health vaccination programs support immune function and reduce concurrent diseases that predispose to endometritis.

Biosecurity for endometritis prevention focuses on reducing bacterial contamination during and after calving. Calving areas should be clean, dry, and well-bedded with frequent bedding replacement. Separating calving areas from sick pens and high-traffic areas reduces pathogen exposure. Equipment used for assisted deliveries must be clean and disinfected between uses. Personnel assisting calvings should practice appropriate hygiene including clean protective clothing and gloves. While endometritis is not contagious in the traditional sense, reducing environmental bacterial load decreases the challenge to the uterine immune system.

Nutritional prevention centers on optimizing transition cow nutrition to support immune function during the critical periparturient period. Adequate energy intake during the dry period and early lactation minimizes negative energy balance that impairs uterine immunity. Protein nutrition supports immune cell function and tissue repair. Trace minerals including selenium, copper, and zinc are essential for immune function and antioxidant defense. Vitamin E supplementation supports immune function and reduces oxidative stress. Avoiding excessive body condition at calving reduces dystocia risk and metabolic problems.

Management practices that reduce endometritis risk include minimizing calving complications through appropriate breeding decisions, heifer development, and calving management. Prompt and hygienic intervention when assistance is needed reduces contamination and trauma. Early identification and treatment of retained placenta reduces the duration of bacterial contamination. Monitoring postpartum cows for discharge and other signs enables early detection and treatment before chronic changes develop. Maintaining detailed records of calving events and postpartum health identifies patterns and risk factors.

Monitoring and early intervention protocols optimize endometritis outcomes. Routine postpartum examinations at defined intervals, such as 21 to 35 days postpartum, identify affected cows early when treatment is most effective. Establishing threshold criteria for intervention, such as discharge character and days postpartum, ensures consistent management. Recording examination findings and treatments enables evaluation of prevention and treatment protocols. Regular review of reproductive performance and postpartum disease incidence identifies opportunities for improvement.

Daily management during the postpartum period should incorporate observation for signs of reproductive tract infection including abnormal discharge. Personnel should be trained to recognize normal versus abnormal postpartum changes and report concerns promptly. Monitoring eating behavior, milk production, and demeanor identifies cows that may be developing health problems. Tail and perineal area observation during milking provides opportunities to detect discharge without additional handling. Fresh cow protocols that include body temperature monitoring help distinguish endometritis from more systemic conditions.

Housing and environmental management influence endometritis risk through effects on bacterial exposure and animal stress. Maternity areas should be designed for easy cleaning and disinfection, with adequate space and comfortable bedding. Fresh cow housing should minimize stress from overcrowding, competition for feed and water, and heat or cold stress. Adequate lying space with clean, dry bedding reduces contamination of the reproductive tract. Good ventilation reduces respiratory pathogen exposure and supports overall health.

Herd health programs addressing endometritis integrate reproductive management with transition cow health protocols. Fresh cow examination protocols define timing and procedures for postpartum reproductive checks. Treatment protocols establish criteria for intervention and standardize treatment approaches. Monitoring key performance indicators including days to first service, services per conception, and pregnancy rate identifies whether current protocols are effective. Integration of veterinary services ensures expert input on complex cases and protocol development.

Record keeping for endometritis management documents individual cases and enables herd-level analysis. Records should include calving date, any complications, postpartum examination findings, treatments, and breeding outcomes. Analysis identifies risk factors specific to the herd, such as associations between specific calving complications and subsequent endometritis. Tracking treatment success rates evaluates protocol effectiveness. Electronic records facilitate analysis and identification of trends requiring intervention.

Economic considerations drive endometritis management decisions in commercial operations. The costs of prevention, including improved calving facilities, nutritional supplements, and postpartum examination programs, must be weighed against the losses from endometritis-related infertility. Treatment costs are generally modest compared to the economic impact of delayed conception. However, cows that fail to respond to treatment and remain infertile represent ongoing costs and should be culled according to established decision points. Economic analysis of reproductive performance identifies opportunities for improvement and justifies investment in prevention and treatment programs.

Among cattle breeds, dairy breeds experience higher endometritis incidence than beef breeds due to the metabolic demands of high milk production and the intensive reproductive management of dairy systems. Holstein cattle, as the predominant dairy breed, account for most documented endometritis cases. The metabolic stress of high production contributes to immune suppression that increases susceptibility to uterine infection. Jersey, Brown Swiss, and other dairy breeds experience similar challenges proportional to their production levels. Within breeds, high-producing individuals are at greater risk than lower producers.

Production system influences endometritis risk more than breed per se. Intensive dairy systems with high production, confined housing, and tight reproductive management see substantial endometritis incidence. Pasture-based systems with lower production and more extensive management may have lower incidence due to reduced metabolic stress and cleaner calving environments. Beef operations have lower endometritis incidence because the animals experience less metabolic stress and have less intensive reproductive management, though the condition does occur and causes fertility losses when present.

Genetic selection for endometritis resistance is possible through selection for related fertility and health traits. Genetic evaluations for daughter pregnancy rate, productive life, and other fertility measures indirectly select for resistance to reproductive disorders. Some breeding programs are developing direct genetic evaluations for metritis and related conditions based on health recording data. Selection for immune function traits may improve resistance to uterine infections along with other infectious diseases. Balancing selection for production with selection for fertility and health maintains overall profitability while reducing disease incidence over time.

Endometritis commonly occurs as part of a complex of postpartum reproductive and metabolic disorders. Metritis, the more severe systemic uterine infection occurring in the first 21 days postpartum, frequently precedes endometritis development. Retained placenta is strongly associated with subsequent endometritis due to the bacterial growth medium it provides and the delay in uterine involution it causes. Metabolic disorders including hypocalcemia and ketosis impair immune function and predispose to uterine infection. Mastitis and other concurrent infections may share underlying immune suppression that also increases endometritis risk.

Several conditions present with similar symptoms or may be confused with endometritis. Normal postpartum lochia in the first two to three weeks after calving involves some discharge that should not be confused with pathological endometritis. Pyometra, accumulation of pus in the uterus with a persistent corpus luteum, presents differently with uterine distension and anestrus. Vaginitis or cervicitis causes discharge originating from sites other than the uterus. Cystic ovarian disease may cause reproductive failure that mimics endometritis effects on fertility. Accurate diagnosis requires careful examination to distinguish these conditions.

Complications and sequelae of endometritis include progression to pyometra if the cervix closes while infection persists, chronic endometritis with permanent endometrial damage, and subfertility or infertility from impaired uterine function. Cows with endometritis are more likely to develop cystic ovarian disease due to disruption of normal reproductive hormone patterns. Repeated episodes of endometritis in successive lactations suggest individual susceptibility and may warrant culling. The extended calving intervals resulting from endometritis have cascading effects on lifetime production and profitability.