Temperature preferences of dairy calves for heated calf hutches during winter in a temperate climate

Newborn calves face challenges adapting from the warm uterine environment to cold ambient temperatures, and often experience cold stress. The objective of this study was to assess the preferred inside hutch temperature of dairy calves in their first week after birth during Central European winter and to compare lying behavior in heated and nonheated hutches. Sixteen matched pairs of dairy calves (2.6 ± 1.3 d old) were enrolled in 7-d replicates with a preference and a control phase. During the preference phase, the calf could choose between 4 different hutches with access to a shared paddock. Inside the hutches, either 0, 1, 2, or 3 heat lamps (HL0, HL1, HL2, HL3) were switched on. The control calf was kept in a nonheated hutch with an enclosed paddock. Calves were observed for 3 to 4 d, then switched from preference to control phase (or vice versa) and observed again for 3 to 4 d. The calves' location was documented once per minute by a time-lapse camera. Lying times and lying bouts were monitored by a 3-dimensional accelerometer data logger attached to the calves' metacarpus. With each additional heat lamp switched on, the temperature inside the hutches rose by 2.6 ± 1.0°C. Calves spent 90% of their time inside a hutch, irrespective of the number of heat lamps switched on, and no preference for a specific inside hutch temperature existed. However, we observed a tendency to prefer the location of the hutches closest to the control calf. Lying behavior did not differ between preference and control phase, but decreased marginally with increasing age. These findings could indicate a need of shelter for calves in winter, but without a preference for a certain inside hutch temperature under the prevailing conditions of deep straw bedding, highly sufficient milk supply, and an ambient temperature of 5.4 ± 3.3°C.