A total of 419 slaughtered cattle were used to investigate the serum Ig G titers to the Mannheimia haemolytica Al whole cell and leukotoxin recognized with important virulence factor in bacterial pathogenesis. Data obtained in this study were represented with average absorbance${pm}$standard deviation. Serum Ig G titers were detected with the ranges from 0.1 to 0.5 at 490nm. Whole cell titers were higher than leukotoxin antibody on the whole. Antibody titers of slaughtered cattle between races, ages have no significant difference but gradual decrease under aging in dairy cow for whole cell (decline mean titer from 0.29 to 0.27 according to age) was undertaken. Holstein bulls shipped from Seoul province had a significantly lower Ig G titers than those from another ones (p<0.05).