Heat stress is an increasing concern for dairy farming in Central Europe. Individual calf housing, while common, can create microclimates that either mitigate or exacerbate the thermal load. The present study was conducted to quantify the effect of housing type (wooden, white plastic, blue plastic) and location (under a shelter vs. outdoors) on the risk of heat stress in pre-weaned dairy calves under typical Central European conditions. A total of 1,200 observations were collected over a year, and the thermal load was assessed using the Equivalent Temperature Index for Cattle (ETIC). Results showed that the housing location was the single most critical factor (shade vs. no shade). All 72 recorded cases of moderate heat stress (ETIC > 26 °C) transpired exclusively in unsheltered, outdoor hutches, with no cases observed under the shelter. Furthermore, within the unsheltered group, housing material was a significant factor in preventing extreme thermal events: while all cases of moderate stress occurred in plastic hutches (40.3% in white, 59.7% in blue), no cases were recorded in wooden hutches. The overall thermal load, measured by the Equivalent Temperature Index for Cattle, confirmed these findings. The three most thermally challenging combinations were statistically grouped (Group a): the unsheltered blue plastic hutches (LS-Mean ETIC = 12.09 °C), the unsheltered white plastic hutches (11.15 °C), and, surprisingly, the sheltered blue plastic hutches (10.46 °C). The LS-Mean for the optimal scenario, represented by the outdoor wooden hutches (8.85 °C), was significantly lower (P<0.0001) than that of the high-risk group. This study provides quantitative evidence that giving shade is the most effective strategy for preventing severe heat stress. When shade is unavailable, using wooden or, to a lesser extent, white plastic hutches is preferable to dark-coloured plastic alternatives. The findings of the present study offer practical, data-driven recommendations for improving calf welfare and management practices on dairy farms in the region.
Havlicek et al. (Thu,) studied this question.