Bulk tank somatic cell count (BTSCC) is the most commonly used measure of udder health on most dairy farms.

There are many reasons that BTSCC is used. High BTSCC is a good indicator of udder health problems on the farm. BTSCC is also readily available. DHIA records provide individual somatic cell count (SCC) as well as a weighted average and provide a fairly accurate measure of BTSCC.

Many co-ops provide BTSCC from every load of milk picked up from a dairy. This data can provide up-to-date SCC data and can also give information about trends in BTSCC. Data from co-op records will not include any cows that are out of the tank. Can a dairy farm have a mastitis problem if the somatic cell count is low?

In Virginia, a SCC of below 250-300,000 cells per milliliter is considered to be good, while a BTSCC of less than 200,000 cells per milliliter is ideal. Economic losses associated with mastitis include death loss, drug treatment costs, veterinarian expenses, milk loss due to waiting for drug withdrawals and future milk production loss due to waiting for drug withdrawals and future milk production loss due to udder damage caused by chronic inflammation. Chronic mastitis causing damage and milk loss has long been considered the primary cause of economic loss.

There are herds that have a low BTSCC but still have a mastitis problem. In addition to monitoring BTSCC daily, managers should also monitor number of cases of mastitis and number of quarter cases. It is difficult to come up with herd numbers for average number of mastitis cases. The number is usually expressed as number of cases per 100 cows per year or per month. The major problem comes in defining a case of mastitis.

Most farms have cows that periodically have a few flakes in the milk. In other cases, there are cows that have a few flakes in the first few squirts of foremilk but then become visually normal after pre-stripping. Farms also vary in how well the milking crew identifies cows with mastitis.

So, how do you know if you have an udder health problem despite a low BTSCC? The only way to know is to keep good records. Records can be kept on paper or entered into the health section of DHIA.

In addition to keeping good records, review them with your herd veterinarian on a regular basis so adjustments can be made to prevention and treatment protocols. PD

John F. Currin
D.V.M.
Extension Veterinarian
Virginia Tech University