Citric acid concentration in subclinical mastitic milk.

The effect of subclinical mastitis on the citric acid concentration of cow's milk was studied by comparing milk from the mastitic quarter with that from a healthy quarter of the same udder. Forty-two pairs of fore-milk from the morning milking of 17 cows were examined and the citric acid content was measured by an automated carboxylic acid analyzer. The citric acid concentration deceased in subclinical mastitic milk and the extent of decrease was proportional to the degree of mastitis as expressed by the quarter difference value in concentration of Na + Cl in mM/l, i.e. the increase in the Na and Cl concentrations in the abnormal milk over that found in normal milk from the same udder. The correlation coefficient between the quarter difference value of Na + Cl and the value for citric acid was -0.77, (d.f. = 46, P less than 0.001) and a linear regression equation was obtained. The result showed clearly that subclinical mastitis is one of the causes of variation in the citric acid content of cow's milk. The quantitative change in citric acid concentration in subclinical mastitic milk is discussed with reference to the admixture theory for the formation of abnormal milk.