Abstract
Data from experiments in 55 commercial herds have been examined to study the patterns of Corynebacterium bovis infection. Such infections are most common in herds that are not subjected to regular control methods but their commercial significance appears to be small. In herds using teat disinfection and dry cow therapy levels of infection with this organism are low. There is no evidence from these data to suggest that C. bovis infections protect the udder against invasion by a major pathogen. On the contrary these infections do not persist when major pathogens invade.