Exploring structural changes in the Swedish cattle population and between-holding movements

Movements of livestock between holdings plays an important role in the spread of many infectious diseases, and network analysis can provide a greater understanding of potential spread dynamics. This study explored cattle movements between Swedish holdings from 2005 to 2022 to enhance the knowledge basis for epidemiological analyses. In addition to classical network analysis, a novel method, Location Change Pattern (LCP), was used to analyse movements between holdings per individual. Furthermore, survival analysis was used to investigate animal- and herd level risk factors associated with moving cattle from a holding. Although the number of cattle and holdings decreased, the number of movements increased substantially over the study period. Simultaneously, the network became more disassortative with an increased average path length, whilst indegree and in- and outgoing contact chains decreased. Combined, the results suggests that an epidemic spread in the cattle population may be slower and reach a smaller final size compared to 2005. Additionally, the clustering coefficient and reciprocity increased over time which might change the dynamics of disease spread. The increase in movements can be partly explained by an increased number of cattle being moved back and forth between holdings, particularly seen for female cattle. Male calves at holdings with a high proportion of female cattle had the greatest hazard of being moved, with an increased hazard at around 20 days of age. In summary, significant changes over time were found in the cattle population and in the movement network, which must be accounted for when working with disease prevention.