Dairy NZ

The SCC can be measured in a number of different ways:

• Cow-side, on an individual quarter basis - using a Rapid Mastitis Test (RMT)
• Herd test sample, on an individual cow basis - known as the Individual Cow SCC or ICCC
• Bulk tank sample, when the tanker empties the vat (per consignment basis) - known as the Bulk Milk SCC or BMCC

Recent developments in milking machine technology have allowed some milking systems to include sophisticated in-line SCC measuring devices.  These should not be confused with technologies that measure changes in milk conductivity, and related measures.

SCC thresholds

The SCC increases when an individual udder or gland becomes infected with bacteria and starts to release somatic cells.  The SCC can rise very quickly, and to very high numbers.

The thresholds at which a gland or cow is considered infected depend on the age of the cow, the number of quarters affected and the way that the milk sample was collected.

Typically a cow or heifer is considered infected if:

• A cow has an ICCC above 150,000/ml (herd test sample)
• A heifer has an ICCC above 120,000/ml (herd test sample)

If the SCC is measured on the first foremilk from an infected gland, the SCC threshold for infection is very much higher (i.e. above 500,000/ml).

Different thresholds are used for the BMCC. A BMCC of 150,000 per ml or less is considered desirable whereas a BMCC above 350,000 or 400,000/ml will usually attract a financial penalty.

Generally the BMCC will be related to the proportion of cows with subclinical mastitis in the herd.  Sudden spikes usually indicate new infections occurring in the herd, some of which will be undetected clinical cases.

What do farmers need to know?

Use SCC information to monitor changes in mastitis of individual cows or for the whole herd. 

• If the BMCC shows sudden spikes on a day to day basis, strip the herd to find undetected clinical cases.
• If the BMCC is approaching 300,000/ml, reduce the number of infected cows in the herd. Get help (vet, farm advisor, dairy company, websites) on ways to find mastitis and reduce the BMCC.
• If the ICCC of individual cows is above 500,000-1 million/ml, strip to find clinical signs.

Only treat cows with clinical mastitis.  It is not cost-effective to treat subclinical mastitis during lactation.  Read more on treating subclinical mastitis.