Coliform Mastitis - the Importance of the Dry Period

Despite significant progress in the control of contagious pathogens, environmental mastitis continues to be a major cause of financial loss to the UK dairy industry. This paper presents some findings from a field study designed to investigate the incidence and significance of coliform infections acquired during the non-lactating period. The bacteriological status of two quarters from each of 629 cows was assessed through the non-lactating period (two quarters were left as unsampled controls); samples were collected from all mastitic quarters of these cows during the subsequent lactation. A significant rise in the incidence of intra mammary infection was detected between drying off and prior to calving. When compared to unsampled controls, quarters sampled during the dry period did not show a significantly different incidence of infection at calving, or subsequent clinical mastitis. Quarters infected with a coliform during the dry period were significantly more likely than uninfected quarters to develop mastitis caused by that pathogen. Of all coliform mastitis occurring in the first 100 days of lactation, 52% arose in quarters previously infected, during the dry period, with the same species/strain of bacteria (as identified by DNA fingerprinting). These findings suggest that management during the dry period may influence the incidence of coliform mastitis in the subsequent lactation.