Bovine Mastitis: A Review

Abstract

The principal organisms associated with mastitis are Streptococcus agalactiae, other streptococci, and Micrococcus pyogenes. They usually cause a chronic mastitis and loss in milk yield with or without clinical symptoms. S. agalactiae can be eradicated from most herds by good sanitation combined with frequent cultural tests and treatment of infected quarters. Organized programs for the control of this form of mastitis have been successful in England, Denmark and the United States. Similar programs were found inadequate for control of other forms of mastitis primarily because present sanitary measures fail to prevent new- and re-infection. In mastitis control due to organisms other than S. agalactiae, treatment is considered to be of questionable value, and a reduction in clinical mastitis by improved management, especially the use of proper milking practices, has been reported. Factors reported as influencing the chances for udder infection to occur are degree of exposure, inherited resistance, age, ability of the teat canal to prevent passage of microorganisms, and prolonged milking. Factors that appear to lower the resistance of infected quarters are chilling, excessive feeding of high protein concentrates, and abusive milking which can result from an excessive vacuum level, prolonged milking, and use of worn or poorly designed teat cup liners. The problem of antibiotics in milk is discussed.