Influence of liver fat on experimental Escherichia coli mastitis in periparturient cows

Eleven cows with a wide range of liver fat (5.7 to 51.4 per cent) at seven days post partum were experimentally infected in a single quarter with a capsular Escherichia coli at 10 days post partum. The results suggested that a fatty liver in itself does not influence the severity of mastitis. All animals had clinical mastitis 10 hours after infection but no animals became severely ill and no treatment was given. Four out of five animals in the group with less than 20.2 per cent liver fat had bacteria in their milk at 10 hours after infection but these bacteria were eliminated by 12 hours. The six animals in the group with more than 28.3 per cent fat in their liver retained viable bacteria in the udder for much longer; with two animals bacteria were shed and abnormal milk was secreted for up to four months despite antibiotic therapy.