Worldwide bovine mastitis (clinical and subclinical) is one of the most important diseases causing considerable economic loss to the farmers in dairy industry. The causative organisms of mastitis are ubiquitous in nature and persist long time in the cow yard or barns. Reduction in milk Production in subclinical mastitis (SCM) is not only a reason of great economic loss to the dairy industry but also acts as a carrier & source of infection for the healthy milch cows which is one of the biggest obstacle in the achievement of self-sufficiency in milk production in Bangladesh. On the other hand, control of this disease by successful treatment in dairy animals depends to a great extent on the type of infection, proper selection & administration of drugs. This book is emphasized on the major bacterial profiles causing different grades of subclinical mastitis along with their isolation, identification and characterization. Find out in vitro the antibiotic sensitivity pattern of the bacterial isolates. This book will provide a clear guideline to the practitioner and policy maker to prevent indiscriminate use of antibiotics and ultimately avoid antibiotic hazard in animal health.