The effect of subclinical mastitis on milk composition in dairy cows

Milk samples were collected from quarters of 35 cows with subclinical mastitis (California mastitis test [CMT] positive and somatic cell counts [SCC] >500,000 cells/ml in individual quarter foremilk), as well as from 37 healthy controls. Compared to the levels observed in milk from healthy quarters, milk from quarters with subclinical mastitis showed elevated sodium (91.97 vs 52.93 mg/dl), chloride (>0.14 vs <0.14 g/dl), pH (6.69 vs 6.59), albumin (5.62 vs 2.65 g/dl), lactate dehydrogenase (LDH) activity (1524.04 vs 485.94 IU/L) and immunoglobulins (26.86% vs 7.43%). In contrast, decreased values were found for calcium (90.45 vs 126.29 mg/dl), inorganic phosphorous (24.40 vs 30.59 mg/dl), potassium (151.56 vs 167.74 mg/dl), α-lactalbumin (22.25% vs 28.72%) and β-lactoglobulin (34.21% vs 57.08%). No changes were seen in blood serum LDH activity. Furthermore, an increase in positive response to CMT was found to be accompanied by an almost proportionate increase in immunoglobulin values to 48.20% and decrease of α-lactalbumin levels in milk serum (P<0.01). These changes in pH, mineral concentrations, LDH activity and protein fractions in milk of quarters show the presence of tissue damage provoked by SCM. Thus, these parameters can be used in the diagnosis of mastitis.