The objective of the study was to estimate the extent to which infection with Mycobacterium avium subspecies paratuberculosis (MAP) of cows in a large dairy was attributable to the infection status of the dam. Data for 625 dam-daughter pairs of Holstein cows were used in a retrospective longitudinal study design. MAP serologic test results were compared for cows and their dams. Logistic regression was used to assess whether a cow's MAP sero-status was associated with her dam's sero-status. Daughters of seropositive dams were 6.6 times more likely to be seropositive, compared with those of seronegative dams. For seropositive cows born to seropositive dams, 84.6% of infection was attributable to being born to a seropositive dam and 15.4% to other exposures, including exposure as calves to flush water that contained feces of adult cattle. For the herd as a whole, infection in 34% of the seropositive cows was attributable to being born to a seropositive dam. For dairy herds that breed back seropositive cows, subsequent transmission of MAP to their daughters, either congenitally or via exposure to feces and colostrum of the dam soon after birth, can contribute significantly to maintaining prevalence of MAP in a herd. Culling of seropositive, nonclinical cows and their daughters is necessary to reduce MAP infection attributable to congenital or periparturient transmission from dam to daughter.