Mastitis, an inflammatory reaction of udder tissue most commonly associated with bacterial infections, is the most common and most costly dairy cattle disease. The inflammatory response consists of an increase in blood proteins and white blood cells (somatic cells) in the mammary tissue and the milk. High quantities of somatic cells in milk dramatically reduce the value of milk to the processor, and often render it unfit for human consumption.

It has been estimated that mastitis costs the dairy industry about $200 per cow per year, and that up to 40% of dairy herds are affected.

Reduced milk production accounts for approximately 70% of the total loss associated with mastitis. Other costs include treatment cost, discarded milk, death and premature culling, decreased genetic advancement, and reduced milk quality. Persistent inflammation can lead to permanent tissue damage and reduced milk yield.

Bacteria, such as forms of Streptococcus and Staphylococcus are by far the most common causes of mastitis. Bacterial infections can be transmitted from one cow to another during milking. Yeast mastitis can be caused by overuse of antibiotics.

The vast majority of mastitis is “subclinical” (symptoms not apparent). For every case of clinical mastitis (severe inflammation, fever, shivering), there are 20-40 times as many cases of subclinical mastitis. Subclinical mastitis may progress and develop into clinical cases, or it may persist for a long time at a subclinical level. Without some form of testing, subclinical mastitis goes undetected.

Somatic cells are a normal constituent of milk and only when they become excessive do they indicate a problem. The udder’s response to infection or injury results in an increase in somatic cells in milk. The number of somatic cells indicates the severity of the mastitis. Measurement of somatic cells (Somatic Cell Count) has become an effective means of detecting subclinical mastitis. Somatic Cell Count (SCC) is expressed as cells/ml of milk.

Milk with less than 200,000 somatic cells/ml is considered the highest quality. Higher counts are considered abnormal and indicate possible infections. To be used for human consumption, milk must have less than 750,000/ml SCC. Milk markets rely routinely on SCC to help ensure good quality milk, and usually pay a premium for milk with low SCC.

THE EFFECT OF AGRASTIM® ON SOMATIC CELL COUNT