[Evaluation of associations between barn characteristics, results of barn climate parameter measurements and health indicators in Swiss veal calf herds].

Introduction: Easy-to-use digital devices to measure climate parameters that can also be used in calf barns have become available commercially in recent years. Data collected in a prospective cohort study in 43 Swiss veal calf operations were evaluated with regard to validity of measured climate parameters, potential associations of those with barn features, and relationships between values of climate parameters and barn characteristics, respectively, with indicators of calf health. Barn parameters, such as ventilation system, access to an outdoor pen and barn size, were recorded, and temperature, air humidity, ammonia and carbone dioxide concentrations were measured at five different locations in each barn during an average of six farm visits over a year. Furthermore, continuous measurements of temperature and humidity (over a period of 72 hours each) were performed once in summer and once in winter in each farm. Whether barn parameters and measured barn climate values are associated as significant risk factors with indicators of calf health (antimicrobial use, mortality and daily weight gain) was explored with statistical methods. Values outside the optimal range were observed for all parameters measured punctually during farm visits and in all seasons. Values of temperature and humidity outside the optimal range were observed more often by continuous than by punctual measurements. Relevant correlations were observed neither among the barn climate values measured punctually nor among measured barn climate values and number of calves, barn surface, bedded surface and barn volume. High maximal group size and presence of mechanic ventilation were positively associated with high antimicrobial use, and high maximal group size and high number of fattening groups were associated with mortality >3%. Farms in lowland regions and high air volume per calf were positively associated with daily weight gain. None of the measured barn climate parameters was associated with the calf health indicators antimicrobial use, mortality and daily weight gain. Therefore, climate parameter measurements appear inadequate to predict calf health in veal fattening operations. The present results show that these (easily) measured parameters are difficult to interpret and should be considered critically.