The activity and reactivity of the hypothalamus-pituitary-adrenal axis (HPA), performances and behavioural characteristics are used as welfare indicators in farm animals. However, to date, relationships between these traits are not well understood yet. Therefore, we used data of general activity, average daily gain (ADG), cortisol responses to ACTH (CR-ACTH) and hair cortisol (HC) of 81 bulls that were collected during an experiment. The aim was to investigate the links between these traits with an exploratory approach, namely by correlation analysis. At 7, 9 and 12 mo of age, the general activity was recorded by accelerometers during 2-3 consecutive days in each period. At 8 mo of age, regrown hip hair, which had been clipped four weeks earlier, was sampled for cortisol analysis. At 11 mo of age, CR-ACTH (1 IU/kg0.75 body weight) was measured. ADG was calculated for 4-week intervals between 7 and 11 mo of age. Data were analysed by Pearson correlations using z-scores. The time spent lying, standing and walking of two consecutive measurement periods were positively correlated (r ranging from 0.39 to 0.57, P<0.05). Greater laytime and walktime at 9 mo were weakly associated with greater and lower ADG at 9 and 11 mo, respectively (r=0.19 (P=0.10) and r=-0.22 (P<0.05)). Greater laytime and walktime at 12 mo of age were related to greater and lower ADG at 11 mo (r=0.22 (P=0.06) and r=-0.27 (P<0.05), respectively). Greater ADG at 10 mo was associated with lower CR-ACTH (r=-0.41 (P<0.01)) and greater ADG at 8 mo with greater HC concentrations (r=0.28, P<0.05). No correlations were found between behaviour traits, CR-ACTH and HC concentration. In conclusion, greater physical activity slightly lowered ADG. Most other relationships were very weak or lacking, even when measurements were close in time to each other. Further studies should investigate if and under which conditions (e.g. time of measurement) welfare indicators show agreement in order to facilitate their use for assessing welfare.
