Bovine mastitis causes severe economic losses in terms of poor milk production and culling of chronically infected animals. In present study milk samples were collected from Cholistani cattle and examined using California mastitis test (CMT). Different milk and blood serum biochemical parameters were investigated. The results indicated that milk pH, milk electrical conductivity, malondialdehyde concentration and total dissolved solids were significantly (P<0.0001) increased with increase in CMT score. The values of milk fat, protein, lactose and solids not fat were significantly reduced in milk samples of sub-clinically infected cattle. The results showed that the values of total milk leukocyte and neutrophil counts were significantly higher in infected cattle, while the percentages of monocytes, macrophages and lymphocytes were lower. The levels of potassium, calcium, magnesium, phosphorous, iron and zinc were significantly lower in milk and blood serum of infected than normal cattle. The enzymes such as aspartate aminotransferase, lactate dehydrogenase and alkaline phosphatase were higher in milk and blood serum of infected animals. Similarly, malondialdehyde and nitric oxide were significantly higher in infected animals. The results showed that mastitis poses deleterious effects on milk and blood of infected animals.

Key words: Biochemical changes, Blood, Cattle, Milk, Somatic cells, Sub-clinical mastitis