Individual and group level health factors influence social networks of dairy calves

Evidence across species supports a relationship between health and social relationships, which may have important welfare implications for intensively housed animals. We evaluated how individual and group-level health factors are related to social behavior of group-housed dairy calves, using social network analysis. Holstein dairy calves (heifer: n = 55; bull: n = 32) were grouped (9 groups; 10 calves/group) at 2 weeks of age until after weaning from milk at 8 weeks of age. To generate social networks, calf positions were recorded continuously using an ultra-wideband positioning system generating undirected pairwise proximity estimates. Individual status and group-level prevalence of clinical respiratory disease, gastrointestinal illness, and lung consolidation were characterized weekly using standard approaches. Mixed-model analysis, following an information theoretic-approach to select predictor values, revealed reduced strength and higher closeness in calves in groups with a higher prevalence of respiratory disease or lung consolidation, whereas individual health status was not a significant predictor. However, eigenvector centrality was lower in calves with lung consolidation during weaning, which was predicted by pre-weaning co-occurrence of respiratory disease and lung consolidation. These results suggest nuance in how multiple health factors, at the individual and group level, influence social network structure in dairy calves.