Endometritis significantly impacts fertility and milk yield, thus reducing profitability of the dairy production. In cows that develop endometritis, normal postpartum endometrial inflammation is dysregulated. Here, we propose that endometrial inflammation is reflected in cervico-vaginal mucus (CVM) which could therefore be used as a prognostic tool. CVM was collected from 20 dairy cows (10 with clinical endometritis and 10 healthy) 7 and 21 days postpartum (DPP). Polymorphonuclear (PMN), mononuclear leukocyte and epithelial cells were counted, total protein levels were estimated and levels of IL-1β, IL-6, IL-8, serum amyloid A (SAA), haptoglobin (Hp) and C5b were analyzed by ELISA in CVM. PMN were consistently high in CVM from 7 to 21 DPP, but were higher in CVM from cows with clinical endometritis 21 DPP compared with healthy cows. In contrast, there were more epithelial cells in healthy cows 21 DPP than in clinical endometritis animals. Total protein levels decreased significantly in CVM from healthy cows between days 7 and 21 postpartum. All inflammatory biomarkers except C5b, remained high in cows with clinical endometritis from 7 to 21 DPP, indicating sustained and chronic endometrial inflammation. IL1, IL-6, IL-8 and Hp levels were higher in CVM from cows with clinical endometritis compared to healthy cows 21 DPP. Interestingly IL-1β levels were raised in CVM from clinical endometritis but not in healthy cows 7 DPP suggesting that early measurement of IL-1β levels might provide a useful predictive marker of clinical endometritis. In contrast, SAA and C5b levels were increased in healthy cows 21 DPP, compared to cows with clinical endometritis suggesting that these acute phase proteins might have an anti-inflammatory role. Our results show that CVM is convenient for profiling disease-associated changes in key inflammatory molecules postpartum and reaffirms that sustained inflammation is a key feature of clinical endometritis in the dairy cow.

IntroductionIn cows, 75% of cases of milk fever, ketosis, displaced abomasum, retained placenta, and uterine infections occur during the first 30 days postpartum (1). Interestingly, bacteria that are isolated from the uterine lumen of 80%-90% of normal cows during the first weeks after calving (2) are responsible for five 'classifications' of uterine infections: puerperal metritis, clinical metritis, clinical and subclinical endometritis, and pyometra.Puerperal metritis presents as a fetid watery-red brown vulvar discharge associated with systemic signs and pyrexia (>39.5 °C) within 21 days of parturition, while clinical metritis presents as a purulent vulvar discharge detected within 21 days postpartum, but without any systemic signs (3). Clinical endometritis is characterized by purulent discharge after 21 days postpartum or a mucopurulent discharge after 26 days postpartum (3). In the absence of any clinical signs, subclinical endometritis is defined according to the stage of postpartum by the presence of >8% neutrophils in uterine cytological samples 21-33 days postpartum, >6% neutrophils at 34-46 days postpartum, or >4% neutrophils after 48 days postpartum (4). Pyometra is characterized by a significant accumulation of purulent material in the uterine lumen combined with a closed cervix and the persistence of a corpus luteum (3).The global incidence of endometritis in cattle is highly variable, ranging from 3.4% to 40%, depending on the diagnostic method (5). Clinical and subclinical endometritis negatively affect the performance of the world's dairy industry; economic losses are related to delay in the resumption of ovarian activity, increased number of services per conception, decreased milk yield, and costs of treatment of the disease (6,7). The United States and Europe have 8.5 and 24.1 million dairy cows and uterine infection costs 650 million dollars and 1.4 billion Euros, respectively (2).Excluding the bovine herpes virus 4 (BoHV-4), a large number of bacteria are responsible for clinical and subclinical endometritis (8,9); these are classified according to their pathogenicity and their frequency of

Cervico-vaginal mucus (CVM), the product of epithelial cells lining the uterus, cervix and vagina, is secreted to facilitate uterine lubrication and microbial clearance. Predominantly composed of water and mucins, CVM also contains high levels of immuno-active proteins such as immunoglobulin A (IgA), lactoferrin and lysozyme which protect against infection by blocking adhesion and mediating microbial killing. The repertoire of cytokines, chemokines and antimicrobial peptides is predominantly generated by the secretions of endometrial epithelial cells into the uterine lumen and concentrated in the CVM. The quantity and relative proportions of these inflammatory biomarkers are affected by diverse factors including the estrus cycle and health status of the animal and therefore potentially provide important diagnostic and prognostic indicators. We propose that measuring molecular signatures in bovine CVM could be a useful approach to identifying and monitoring genital tract pathologies in beef and dairy cows.