Conditions concerning group size, composition/homogeneity and stability may have influence on the success of rearing calves in groups. Introduction of calves into groups do determine not only age dispersion, but do also influence hygiene and patterns of disease transfer. Previous results indicate that large groups may increase the morbidity however we do not know the effect of moderate group size (6-8).

The objective of present study was to achieve increased knowledge in how introduction of calves into group housing systems did influence young calf performance. The present study compare data from calves in groups where new calves were continuously introduced (dynamic groups) and from calves in stable groups were all calves were introduced simultaneously (“All in all out”). The following hypothesizes was tested: “All in all out” introduction of calves into group housing systems is expected to have a positive influence on calves health and growth compared to continuous introduction of calves.