This work consists of two collaborative research projects between INRA (France) and MTT (Finland) that examine the influence of group management on young cattle. The first work investigated whether pair versus individual housing of calves reduces their chronic stress reactions and whether positive contacts with humans could partly compensate for a lack of contact with conspecifics. In the second work, pair-housed heifers were either repeatedly regrouped or kept with their familiar peer. The consequences of repeated regrouping on heifers social behaviour, emotional reactivity, physiology and production were analysed. Calves housed in pairs seem less stressed than calves housed individually, and regular positive contacts with a stockperson can not compensate for the lack of social partners. Pair-housed calves are less ready than their individually housed counterparts to approach humans. However, positive contacts with the stockperson make calves less fearful of people and improve handling both in the individual and pair-housing. Heifers housed in pairs and repeatedly regrouped are more aggressive between each other than heifers kept with the same penmate. However, repeated regrouping lowers heifers behavioural reactivity in comparison with rearing heifers in stable pairs. Therefore, diversity in the social environment rather than stability appears to be more advantageous for heifers. In conclusion, group housing is beneficial for the welfare of calves and a variety of social experiences with conspecifics offers advantages for heifers. Cattle of different ages seem to have different social needs that must be fulfilled to ensure their welfare.