Relationship between serologic recognition of Escherichia coli 0111:B4 (J5) and clinical coliform mastitis in cattle.

Serum IgG1 ELISA titers recognizing gram-negative core antigens (Escherichia coli [J5]) were studied at a large dairy in central California. Population mean log10 titer was 2.7357 (equivalent to 1:544) with a SE of 0.03843. Titers increased with increased lactation number (unstandardized regression coefficient = 0.06733). Changes in lactation number accounted for only 6.77% of titer variation. Titers less than 1:240 were associated with 5.33 times the risk of clinical coliform mastitis. Also, older cattle were at greater risk to develop clinical coliform mastitis. These factors apparently affect incidence in a nonlinear fashion, with greatly increased risk associated with titers less than 1:240 and with fourth or greater lactations.