FAILURE OF EXIT-RACE TEAT SPRAYING TO CONTROL CORYNEBACTERIUM-BOVIS COLONIZATION

When an automated exit-race teat sprayer replaced a conventional teat dip cup for the application of a disinfectant containing 0.5 per cent iodine, there was an increase in the level of intramammary infection b y Corynebacterium bovis at drying off from approximately 25 per cent o f quarters to approximately 75 per cent of quarters, When the peak lev el of infection had been reached half of the clinical mastitis in the herd was caused by C bovis, and these were recurrent and chronic infec tions, There was some evidence that the increase in C bovis infection increased the bulk milk cell count, There were no changes in the rates of infection by major pathogens or by coagulase-negative staphylococc i, another important secondary pathogen, The reintroduction of teat di pping rapidly reduced the rate of mastitis infection and the level of infection was reduced to approximately 20 per cent of quarters in abou t 12 months.