Date of this Version
Preventive Veterinary Medicine 112 (2013) 318– 329
tWe present the first comprehensive description of how shipments of cattle connect thegeographic extent and production diversity of the United States cattle industry. We built anetwork of cattle movement from a state-stratified 10% systematic sample of calendar year2009 Interstate Certificates of Veterinary Inspection (ICVI) data. ICVIs are required to certifythe apparent health of cattle moving across state borders and allow us to examine cattlemovements at the county scale. The majority of the ICVI sample consisted of small ship-ments (<20 head) moved for feeding and beef production. Geographically, the central plainsstates had the most connections, correlated to feeding infrastructure. The entire nation wasclosely connected when interstate movements were summarized at the state level. At thecounty-level, the U.S. is still well connected geographically, but significant heterogeneitiesin the location and identity of counties central to the network emerge. Overall, the networkof interstate movements is described by a hub structure, with a few counties sending orreceiving extremely large numbers of shipments and many counties sending and receiv-ing few shipments. The county-level network also has a very low proportion of reciprocalmovements, indicating that high-order network properties may be better at describing acounty’s importance than simple summaries of the number of shipments or animals sentand received. We suggest that summarizing cattle movements at the state level homoge-nizes the network and a county level approach is most appropriate for examining processesinfluenced by cattle shipments, such as economic analyses and disease outbreaks.