Dairy calf management, morbidity and mortality in Ontario Holstein herds. IV. Association of management with mortality

Associations between heifer calf management and mortality were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. At the farm level, data were stratified by season, with two six-month seasons (winter and summer) per year. The odds of farms with particular management strategies having above-median morbidity were calculated. At the individual calf level, the odds of a calf being treated, controlling for farm of origin and month of birth, were calculated for different management practices. Larger farms had significantly greater odds of experiencing mortality than smaller farms in both winter and summer. Farms which had policies of attending calvings and ensuring that calves received their first colostrum had significantly lower odds of experiencing winter mortality than farms which did not have these policies. Farms which housed calves in hutches had significantly lower odds, and those which housed calves in group pens had significantly higher odds, of experiencing summer mortality, than farms which used individual indoor calf-pens. A policy of teat removal between four weeks of age and weaning was associated with increased odds of summer mortality. At the individual calf level, calving ease, sire, navel treatment, assistance at first colostrum feeding, administration of vitamins A, D and E and anti-scour vaccines to the pregnant dam, and place of calving, were all associated with significantly altered odds of dying. However, several interactions entered the statistical models, and the effects of those management practices were not all straightforward.