The study was conducted on a total of 592 buffaloes and 453 cattle in their different stages of lactation to investigate the biochemical changes occurring in milk due to mastitis. California Mastitis Test (CMT) was used to diagnose the mammary gland infection. The results revealed significant (P<0.0001) increase in pH, electrical conductivity, malondialdehyde and total dissolved solids, while decrease in fat, protein, lactose and solids not fat in milk samples of both mastitic buffaloes and cattle. The total somatic cell and neutrophil counts were significantly higher, while the macrophage and lymphocytes were lower in the milk of mastitic animals. The enzymes including lactate dehydrogenase, aspartate aminotransferase and alkaline phosphatase along with sodium were significantly higher in mastitic than healthy buffaloes. It was similar in cattle as well with the exception of aspartate aminotransferase which was non-significant in cattle. The values of potassium, phosphorous, calcium, magnesium, zinc and iron were significantly higher in the milk of mastitic animals. The copper levels were significantly (P<0.0001) lower in mastitic than in healthy buffaloes, while it showed non-significant difference in cattle. The investigation of enzymes, lipid peroxidation product and milk electrical conductivity in present study appeared suitable diagnostic tools for identification of mastitis.

Key words: Biochemical changes, Buffalo, Cattle, Mastitis, Milk