The level of oxidative stress and antioxidant status in the sub-clinical ketosis were determined as a mean to understand the increase in susceptibility to sub-clinical mastitis. Of the seventy samples of milk and urine collected from the suspected cases of sub-clinical ketosis, fifty samples were found positive for the presence of ketone bodies which confirms the condition of sub-clinical ketosis. Among the above fifty samples, twenty five samples were found positive for sub-clinical mastitis

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... terms of somatic cell count and bacterial culture. Lipid peroxides and the activities of superoxide dismutase, catalase, and glutathione peroxidise were significantly more in those twenty five cases. The level of glutathione was significantly high where as the level of ascorbic acid is significantly less. Thus, in the condition of subclinical ketosis, the alteration of antioxidant status and existence of oxidative stress can make the peripartureant animals susceptible to infectious diseases.