Abstract: | The nonlactating mammary gland was experimentally inoculated with Escherichia coli. During the first half of the nonlactating period, 32% of 34 inoculated glands were temporarily infected. All intramammary infections were eradicated by the cow without therapy and no signs of mastitis were observed. During the 30 days before parturition occurred, 88% of 42 inoculated glands in the cows became infected. Twenty-three intramammary infections were eradicated by the cow and infection in 14 glands persisted after parturition occurred. Peracute toxic mastitis occurred in those cows with infected glands. |