Two- and three-breed crosses among Ayrshires, Brown Swiss, and Holsteins were compared to contemporary purebreds for the effect of crossbreeding on the incidence and severity of diseases. Twenty-two measures of health were used for calves (birth to first calving) and 21 for cows in first lactation. Illnesses per 100 calves were 64, 78, and 140 for Ayrshires, Holsteins, and Brown Swiss, respectively. The two- and three-breed crosses had similar frequenties of calfhood health problems, but both had less than parental means. During first lactation, the two- and three-breed crosses had more health problems than the parental means, thus some heterosis for resistanee to calfhood health problems but not for those occurring in first lactation. Losses of females born alive prior to first calving were 3% less in crosses than in purebreds, but first lactation losses were similar. Seasonal effects were important in both calfhood and cow health problems. Viability from 150 days of pregnancy of dam through first lactation of offspring for 142 two-breed crosses averaged 1% more than the parental mean, whereas the 128 three-breed crosses were less viable (−4%) than the mean of 155 purebreds. © 1968, American Dairy Science Association. All rights reserved.
