Neutrophils are terminally differentiated cellular components of the innate immune system. Neutrophils are the first line of immunity against most pathogens that infect cattle and buffalo. The cytokine and hormonal milieu of the blood and the extracellular tissue fluid can influence neutrophil development and immunity related activities, but the molecular basis of these phenotypic changes and physiological benefits or drawbacks of them are poorly understood. Parturition in dairy animals impairs of polymorphonulcear neutrophil leucocytes activity and with a decrease in the ability to fight bacterial infections. Glucocorticoids have been found to orchestrate various adaptive changes around parturition. This book will help to researcher to know the entire neutrophil system in terms of phagocytic, chemotaxis, enzymatic activity and expression of genes act during this critical period and what changes occur in the neutrophilic numbers, secretary activity and expression during parturition.