What is mastitis?

Mastitis is inflammation of the mammary gland.

In cows, nearly all mastitis is caused by bacteria which have entered via the teat canal.

Once in the udder, these bacteria multiply - commonly resulting in an infection and an inflamed udder.

What different forms of mastitis are there?

Broadly speaking, we recognise three forms of mastitis - severe mastitis, clinical mastitis, and subclinical mastitis.

In severe cases of mastitis, the cow is often very ill (some cases can be life threatening), and the milk is often very watery or blood stained.

Clinical mastitis is the more "normal" mastitis in which the cow is often quite healthy or only very mildly affected in herself, but the udder may have varying degrees of heat, pain and/or swelling and the milk is usually either watery or has clots in it.

Subclinical mastitis is exactly as the name suggests - there are no clinical signs! The cow is healthy, the udder is normal, the milk has no visible changes, but it has a high cell count when tested.

It is important to realise that these are not necessarily different diseases, they are just different expressions (or severity) of the same disease, in just the same way that some humans who contract influenza become severely ill, yet others contracting exactly the same influenza virus can be much less affected.

How much mastitis is too much mastitis?

Whilst many of us think that any mastitis is too much mastitis, realistically we have to accept that there will always be some level of mastitis occurring in a herd - both as clinical cases, and as high cell count cows.

Countdown has given the Australian dairy industry a very useful set of trigger points at which it is suggested that a problem may exist and that immediate action is required.

In terms of clinical cases, the triggers relate to the number of clinical cases at calving, and the number of clinical cases during lactation.

For clinical cases at calving, the trigger point is exceeded if you have -

  • more than 3 clinical cases per 50 cows calved (i.e. cows that have a clinical case within the first 14 days after calving)

For clinical cases during lactation, the trigger point is exceeded if you have -

  • more than 2 clinical cases per 100 cows during lactation (i.e. in cows that have been calved more than 2 weeks).

In terms of cell counts, different herds have different goals, but logically, if you are not receiving premium payment for your milk for the whole year, there is an opportunity for you to lower your cell counts.

Our experience at Dairy Focus is that once farms become "low risk" for mastitis with an effective mastitis control program, the levels of mastitis that occur are well below these trigger points.

However, farms that are currently exceeding these trigger points are most likely to need a mastitis investigation to understand what is causing the problem, and then decide the best way to deal with it.

Knowledgebase categories


General information about mastitis - what is it, what causes it, what does it cost?


How does the milking process influence the risk of mastitis?


What factors influence the risk of mastitis around calving?


How does the dry-off process influence the risk of mastitis in the dry period and at calving?


How can you minimise the effect of the environment?


When to cull, who to cull, how to choose?

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