Fig. 4

The exact incidences of tail injuries (number of tail injuries/number of slaughtered) for the four individual buildings, as well as merged for the whole herd. The comparison period before the trial corresponded to 2017–2020.The adaptation period was from January to June 2021. The trial period was from July 2021 to June 2022. The post-trial period was from July to December 2022. The stars in the figure represent significant differences compared to the comparison period within unit (χ²-tests; *P < 0.05; **P < 0.01; ***P < 0.001). At herd level, the incidence of tail injuries during 2017–2020 was higher (P < 0.01 to < 0.0001, Kruskal–Wallis test) than during the other periods. The overall level of tail injuries was also higher (P < 0.01) during the adaptation period compared to the trial period