Dairy calf mortality rate: the association of daily meteorological factors and calf mortality.

The number of dairy heifer calves born each day, the number of these calves which died prior to 36 days of age and the actual date of death were recorded and analyzed for possible associations with weather factors. The demographic data on dairy calves were supplied by 16 farms in Tulare County, California for the months of July to December 1973. High temperatures in the summer and low temperatures in the winter were associated with an increased risk of death. Calves born during the periods of extreme temperatures had a higher risk of death than those born on more temperate days, while death, when it occurred was temporally related to days of extreme temperatures. Periods of increased risk of death often were associated with large temperature fluctuations irrespective of the absolute temperature. Nonmeteorological factors specific to invidual farms also appeared to influence daily calf mortality rates.