Reproductive tract defense and disease in postpartum dairy cows.

This paper briefly reviews recent data and concepts on the development and mitigation of infection and inflammation in the reproductive tract of dairy cows during the first 2 mo after calving. The incidence of metritis is typically between 10 and 20%, of clinical endometritis or purulent vaginal discharge (PVD) approximately 15%, and of subclinical or cytological endometritis a further 15%. Worse postpartum negative energy balance is associated with more severe or prolonged uterine inflammation. Changes in feed intake, expression of genes for pro-inflammatory cytokines, notably interleukin (IL) 1, IL6 and IL8, circulating concentrations of beta-hydroxybutyrate (BHBA) or nonesterified fatty acids (NEFA), and innate immune function precede both metritis and endometritis by several weeks. Infections with Escherichia coli and Arcanobacterium pyogenes are associated with both metritis and PVD. There are new data to suggest that specific virulence factors in E. coli associated with adherence may be important in metritis and PVD. Cytological endometritis and PVD are overlapping but largely distinct conditions, and there are emerging data that cervicitis exists both concurrent with and separate from endometritis. Much remains to be learned about what initiates and sustains harmful inflammation of the reproductive tract. Such information is necessary to develop effective treatments for the various forms of disease and, more importantly, to develop means to prevent endometritis and cervicitis. In particular, vaccination against specific uterine pathogens and interventions to modulate innate immune response appear to be important avenues for investigation. Presently, commonly recommended best management practices for cows in the transition period are likely to be helpful to mitigate the risk of reproductive disease.