Epidemiological studies of calf respiratory disease in a large commercial veal unit

Records of treatments for respiratory disease among 952 calves in a large intensive veal unit were analysed. The frequency of disease was heavily age-dependent in the 34 batches of 28 calves with a peak at five weeks of age and little disease before the fourth or after the eighth week. The effect was evident for all of the three indices of disease examined: the numbers of first treatments, numbers of new courses of treatment and the total number of treatments. Transient synchronisation of outbreaks of disease in separate batches was observed but attempts to correlate the level of disease with climatic events, using data from local meteorological stations, were unsuccessful. Disease was shown to be clustered within crops of calves at one end of the housing or the other, indicating that contact spread may have been important. A variation in the amount of disease on each day of the week may have been attributable to restricted feeding on Sundays.