Effect of age. A. Upper left panel - hazard of becoming a shedder (gray line) and becoming a high shedder (dark line). The hazard increases rapidly at the age of two, which is first measurement for most cows. The shedding hazard increases significantly before the high shedding hazard. Following the initial rise, the hazard decreases slowly. B. Upper right panel. The population was divided into three groups: young cows (less than three years) adult cows (3–5 years), and old cows (above 5 years). Young cows have a much longer time to high shedding than old or adult cows. C. Lower left panel - negative correlation between age of onset of shedding and time to high shedding. The line represents a linear regression. The correlation is highly significant (p < 1.e-8). D. Lower right panel. Fraction not reaching high shedding for young and adult intermittent shedder (thick lines) and for young and adult continuous shedders (thick gray lines). The young continuous shedders survive longer than adult shedders, but less than intermittent shedders.