Interbreed Matings in Dairy Cattle. II. Herd Health and Viability

Two-and three-breed crosses among Ayr-shires, 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 frequencies 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 resistance to calfhood health problems but not for those occurring in first lactation.Losses o£ 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 threebreed crosses were less viable (--4%) than the mean of 155 purebreds.The annual loss in value of milk stemming from mastitis, ketosis, and milk fever in U.S. dairy herds has been estimated as more than 384 million dollars (19), which is more than 8% of the total annual returns from sale of whole milk.Mastitis alone accounts for more than 95% of these losses.Reduction in milk yield from other diseases, plus the cost of drugs and treatments, make the losses even more staggering.Certain reports (5, 7) suggest that crosses among dairy breeds require less veterinary treatment than purebreds, but they give no indication of wherein the advantage may lie, i.e.,