There are many different factors that go into considering which cows are to be culled - mastitis control is only one of those factors.

In terms of mastitis, culling can mean different things to different farms and even to different cows.

For example, it is possible to cull a cow, cull a quarter (by making her a 3-teater), or cull a cow from the normal milking routine to reduce the risk of spread.

Culling a cow from the farm is the lowest risk strategy, as it completely removes the risk of spread of infection from that cow, and removes her effect on the farm's milk quality.

However, it also removes her production from the farm output, and removes her breeding potential from the herd.

Culling a quarter reduces the risk of spread from that quarter, retains the production on the farm (in general, a cow will produce as much as a 3-teater as she would from all four quarters) and retains the cow's breeding potential.

However, culling the quarter to create a 3-teater increases the risk of inadvertent application of the cups onto the affected quarter, and adds complication to the milking routine.

The effect and risks from culling a cow from the normal milking routine varies depending on the method.

For example if the cow is milked last, or in a separate herd, there is a different set of risks to "putting her on the bucket" during milking. Either way, milking management needs to address those risks.

So the meaning of "culling" can vary from farm to farm, and even cow to cow - it all depends on what the desired outcome is, and the risk managment that is put in place.