Factors Affecting Milk Somatic Cells and Their Role in Health of the Bovine Mammary Gland

¹ Metabolic Diseases and Immunology Research Unit, National Animal Disease Center, USDA-Agricultural Research Service, Ames, IA 50010-0070
² Immunology Group, Agricultural Research Division, American Cyanamid Co., PO Box 400, Quakerbridge Road, Princeton, NJ 08543-0400

Milk somatic cells play a protective role against infectious disease in the bovine mammary gland. Many genetic and environmental factors affect the number and kinds of leukocytes that account for the vast majority of somatic cells in milk. Neutrophils constitute the vast majority of somatic cells in mammary glands that are infected with mastitis pathogens. The recruitment of neutrophils into the infected mammary gland is a normal part of the cow's defense mechanisms that is very effective for eradicating the majority of infections that occur. For many reasons, milk production and milk quality are negatively impacted by the presence of inflammation in infected glands. Because of the negative effects of high SCC in milk, various approaches are needed to reduce milk SCC. In the future, genetic gains for milk quality and mastitis resistance may be made by removing bulls from breeding programs when their daughters are predisposed to high SCC.

Key Words: mastitis • somatic cells • neutrophils • mammary gland

Submitted on February 12, 1993
Accepted on August 12, 1993

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