Reproductive performance drastically declines if a cow with subclinical mastitis later becomes clinical. According to University of Tennessee research published in the June Journal of Dairy Science, subclinical cows that subsequently developed clinical mastitis experienced 110.6 more days open and almost three more services per conception than uninfected animals. "Subclinical mastitis, followed by clinical mastitis, resulted in the most severe loss in reproductive performance," the researchers conclude.

The table below summarizes some of the results.