Somatic cells are always present in milk. A series of bulk milk somatic cell counts (SCC) should be reviewed to see both the level and trend for a herd. Cows regularly shed a small number of cells in their milk. In mid lactation, normal milk can contain 20,000 to 150,000 cells/mL.
There should be concern once a cow has between 120,000 and 150,000 somatic cells in every millilitre of milk it produces. The higher the somatic cell count the worse the infection.
Why is this important?
- A high SCC indicates a high level of mastitis (usually subclinical) in the herd
- About 15% of cows have (subclinical) mastitis for every 100,000 cells/ml
- Sharp rises often indicate missed clinical cases
- Impact of mastitis on SCC is more pronounced when fewer cows in-milk e.g. at the start or end of season
If your SCC exceeds your dairy company's penalty level, individual cow counts can be used to identify offending cows. Milk from these cows can be withheld from the vat until the cows are cured and their SCC lowered.
In all herds, a sudden increase, of 50,000 cells/mL or more, may indicate that one or more clinical cases have been missed. The impact will be more pronounced for smaller herds, or when there are fewer animals in the herd, such as at the start or end of the season.
Herds with a higher SCC may have more fluctuations of the SCC on a day-to-day basis because there will be many more infected quarters.
On average, there are 15% of cows infected for every 100,000 cells/mL up to 300,000 cells/mL.