Mapping U.S. cattle shipment networks: Spatial and temporal patterns of trade communities from 2009 to 2011.
The application of network analysis to cattle shipments broadens our understanding of shipment patterns beyond pairwise interactions to the network as a whole. Such a quantitative description of cattle shipments in the U.S. can identify trade communities, describe temporal shipment patterns, and inform the design of disease surveillance and control strategies. Here, we analyze a longitudinal dataset of beef and dairy cattle shipments from 2009 to 2011 in the United States to characterize communities within the broader cattle shipment network, which are groups of counties that ship mostly to each other. Because shipments occur over time, we aggregate the data at various temporal scales to examine the consistency of network and community structure over time. Our results identified nine large (>50 counties) communities based on shipments of beef cattle in 2009 aggregated into an annual network and nine large communities based on shipments of dairy cattle. The size and connectance of the shipment network was highly dynamic; monthly networks were smaller than yearly networks and revealed seasonal shipment patterns consistent across years. Comparison of the shipment network over time showed largely consistent shipping patterns, such that communities identified on annual networks of beef and diary shipments from 2009 still represented 41-95% of shipments in monthly networks from 2009 and 41-66% of shipments from networks in 2010 and 2011. The temporal aspects of cattle shipments suggest that future applications of the U.S. cattle shipment network should consider seasonal shipment patterns. However, the consistent within-community shipping patterns indicate that yearly communities could provide a reasonable way to group regions for management.
Department of Biology, Colorado State University, Fort Collins, CO, USA. Electronic address: eringorsich@gmail.com.
Erin E
EE
Gorsich
Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT, USA.
Angela D
AD
Luis
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA; Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
Michael G
MG
Buhnerkempe
USDA APHIS Veterinary Services, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
Daniel A
DA
Grear
USDA APHIS Veterinary Services, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
Katie
K
Portacci
USDA APHIS Veterinary Services, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
Ryan S
RS
Miller
Department of Biology, Colorado State University, Fort Collins, CO, USA.
Colleen T
CT
Webb
D000822:Animal Husbandry / Q000191:economics / Q000379:methods*; D000818:Animals; D002417:Cattle; D003132:Commerce; D005260:Female; D008137:Longitudinal Studies; D008297:Male; D008962:Models, Theoretical; D012621:Seasons; D062206:Spatial Analysis; D014186:Transportation; D014481:United States
Cattle shipment; Community detection; Dynamic network; Interstate Certificate of Veterinary Inspection; Network analysis; U.S. cattle industry