Mastitis, metritis and retention of fetal membranes are diseases that may affect any species, but are of greatest economic importance in the dairy cow. On a herd basis, the only significant causes of mastitis is bacteria. Mastitis is considered subclinical when milk has an elevated cell count, with or without isolation of a bacteriological agent.
Contaminants enter the uterus during parturition and establish infection.
Delayed uterine involution is the major predisposing factor and is often accompained by retention of fetal membranes . Endometritis can also results from pyometra or by introduction of pathogens during insemination. Infections with Pasteurella spp, Bacillus spp, Pseudomonas spp, streptococci and stafilococci cause acute metritis, but are the predominant factor in the onset of chronic metritis and endometritis . If we have some doubts in the human being, more difficulties are in the Bovine Immunity System, where there are others endogenous inhibitor.