FACTORS AFFECTING MILK SOMATIC-CELLS AND THEIR ROLE IN HEALTH OF THE BOVINE MAMMARY-GLAND

Milk somatic cells play a protective role against infectious disease i n the bovine mammary gland. Many genetic and environmental factors aff ect the number and kinds of leukocytes that account for the vast major ity of somatic cells in milk. Neutrophils constitute the vast majority of somatic cells in mammary glands that are infected with mastitis pa thogens. The recruitment of neutrophils into the infected mammary glan d is a normal part of the cow's defense mechanisms that is very effect ive for eradicating the majority of infections that occur. For many re asons, 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 m ilk SCC. In the future, genetic gains for milk quality and mastitis re sistance may be made by removing bulls from breeding programs when the ir daughters are predisposed to high SCC.