Clinical and subclinical uterine disease is associated with subfertility and infertility. At the herd level, it is characterized by a longer interval from calving to first insemination or conception in affected animals, and more cows are culled for failure to conceive in a timely manner. These effects on fertility and treatment costs mean that uterine disease is one of the most expensive conditions challenging the dairy industry. In addition, the high incidence of uterine disease in cattle compared with other domestic species suggests that there may be a serious flaw in dairy cow husbandry, or a fundamental problem in some breeds of cattle. Therefore, considerable effort is needed to understand the risk factors for uterine disease and the biological mechanisms of how the uterus is able to detect infection, respond to microorganisms, and how infection regulates normal uterine function.

In a typical study, cows with endometritis had a lower first service conception rate (29.8% vs. 37.9%), a longer median interval to conception (151 vs. 119 days), and more animals were culled for failure to conceive (6.7% vs. 3.8%), compared with unaffected animals. Likewise, cows with purulent cervical discharge had lower calving rates, lower pregnancy rates and more culls without pregnancy. The economic losses associated with uterine infection depend on treatment costs, reduced milk production and infertility. In the UK, the direct costs of treatment and reduced milk production in cows with uterine disease are about €91 1 and uterine disease causes an average loss of about 300 litres of lactation. The indirect costs of longer calving intervals, increased culling rates, additional inseminations and lower estrus expression are €101 per cow, for a total cost of €192 per animal. Based on information from 21 dairy herds in the UK, the direct costs of uterine disease alone were estimated to be €1059 per 100 cows per year, for which data were intensively recorded between 1989 and 1999. There are 19.5 × 10 6 dairy cows in the EU15, and on this basis it is predicted that the direct costs of uterine disease would exceed €206 million. Of course, the indirect costs of the disease would more than double this amount.