Spatial analysis of cattle movement patterns in Portugal.

The network of animal contact through movement is an important factor in disease spread within and between populations. The objective of this study was to characterise the spatial and temporal distribution of bovine movements in Portugal, identifying 'local' and 'long-distance' networks on the basis of geographical proximity. Data were obtained from cattle movements in 2005, as recorded in the national database for bovine identification and registration. Geographic information systems were used to represent distribution and flow of movements. Results did not detect any significant temporal variation either in the number of movements or animals moved. Holdings showed a higher density in the north where a larger number of movements occurs. On the contrary, larger shipment lots tend to occur in the south-central area. The greatest number of movements occurs inside and between contiguous districts; animal movements mostly follow a south-north pattern. Records analysed revealed that 60% of the animals in circulation are beef cows under the age of 10 months (only 31% of the registered animals are younger than 12 months of age).