SYMPOSIUM - MASTITIS AND GENETIC EVALUATION FOR SOMATIC-CELL COUNT - PHYSIOLOGY OF MASTITIS AND FACTORS AFFECTING SOMATIC-CELL COUNTS

Inflammation of the mammary gland that results from the introduction a nd multiplication of pathogenic microorganisms in the mammary gland is a complex series of events leading to reduced synthetic activity, com positional changes, and elevated SCC. The magnitude and temporal relat ionships of these responses vary with nutritional status, other animal factors, and the pathogen involved. Because the elevation of SCC is a response to an insult to the mammary gland and is modulated by inflam matory mediators, the major factor influencing SCC is infection status . The effects of stage of lactation, age, season, and various stresses on SCC are minor if the gland is uninfected. Except for normal diurna l variation, few factors other than infection status have a significan t impact on milk SCC.