Triacylglycerol fatty acid composition of milk from periparturient cows during acute Escherichia coli mastitis.

Changes in fat concentration and triacylglycerol fatty acid (TGFA) composition were studied in milk from six periparturient cows 1 d before and 20 d after an experimentally induced Escherichia coli mastitis in the fore and rear homolateral quarters. Opposite fore and rear heterolateral quarters remained uninfected and were used as controls. Milk was collected from all individual quarters during the experiment. The fat concentration in milk from infected quarters did not change, but total fat production decreased owing to reduced milk production after the Esch. coli challenge. In milk from the heterolateral uninfected quarters fat concentration rose significantly 48 and 72 h after induction of mastitis, the rise being concomitant with a decrease in milk production. Throughout the experiment similar changes in TGFA composition were observed for both infected and uninfected quarters. There was an increase in all the even, odd-numbered, iso and anteiso short-chain TGFA from day +6 on after induction of mastitis. There was little change in the composition of 16:0 and 18:0 fatty acids, while the long-chain unsaturated fatty acids decreased. Using multivariate analysis, the results are presented visually. The observed changes in the TGFA can be ascribed to changes normally observed in cows' milk soon after parturition.