After calving until last 2 – 3 months of lactation
During lactation, cows can become infected with both contagious and environmental mastitis organisms.
Contagious mastitis is caused by bacteria such as Staph. aureus and Strep. agalactiae that are transmitted between cows during milking.
Although Strep. uberis is classified as an environmental pathogen, it sometimes behaves like other contagious mastitis pathogens – that is, it can be transmitted between cows during milking. Milk from one infected quarter is spread to the teat skin of other quarters and cows by milkers’ hands, liners and cross flow of milk between clusters.
Damaged teat ends are particularly susceptible. Malfunction or poor use of the milking machine can contribute to transmission of infection.
Prevention of contagious mastitis involves disinfection of teat skin after milking, wearing clean gloves during milking, careful use of machines that are operating well, and keeping cows calm and teat ends healthy.
Environmental mastitis is caused by bacteria such as E. coli and Strep. uberis. The primary source is faeces and mud. The infection pressure from these bacteria increases when there are wet and dirty environmental conditions.
High traffic areas such as water troughs, gateways, collecting yards and housing areas must be kept clean to minimise infection. Cubicles and calving boxes must be managed to ensure a high level of cleanliness.
Prevention of environmental mastitis involves minimising the build-up of mud and manure in the cows’ environment ensuring clusters go on clean, dry teats.