For me, udder health is the outcome of the interaction of many simple things of how cows are managed, such as aspects of milking, milking machine, immunity, environment, and the transition period.
Bacteria are everywhere on and around the cow and can’t be eradicated. If given the opportunity, some bacterial species will always try to infect the udder because for them, milk is an ideal medium to eat, drink and multiply. But these bacteria are not the cause, they just mirror the flaws in management that allows them to jump from udder to udder or from the environment into the udder. Farmers get the mastitis causing bacterial guests they invite for by the way they work.
The basis for control is understanding the cause (management) and effect (mastitis) relationship of udder health and requires basic education. If this is understood, the rest is about changing attitude and behaviour.
To survive, dairy farms will have to milk more cows over time. Then, doing simple things right becomes more important to compensate for increased infection pressure, due to more animal contacts and more healthy animals being sensitive to infection. On large farms, farmers see they can no longer survive without an attitude allowing strict compliance to standard operating procedures, ensuring simple things are done right to control udder health.