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Network analysis and optimization of animal transports
University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about animal transports and their effect on animal welfare. Transports are needed in today’s system of livestock farming. Long transports are stressful for animals and infectious diseases can spread via animal transports. With optimization methods transport times can be minimized, but there is a trade-off between short distances for the animals and short distances for the trucks. The risk of disease spread in the transport system and disease occurrence at farms can be studied with models and network analysis.

The animal transport data and the quality of the data in the Swedish national database of cattle and pig transports are investigated in the thesis. The data is analyzed regarding number of transports, number of farms, seasonality, geographical properties, transport distances, network measures of individual farms and network measures of the system. The data can be used as input parameters in epidemic models.

Cattle purchase reports are double reported and we found that there are incorrect and missing reports in the database. The quality is improving over the years i.e. 5% of cattle purchase reports were not correctly double reported in 2006, 3% in 2007 and 1% in 2008. In the reports of births and deaths of cattle we detected date preferences; more cattle births and deaths are reported on the 1st, 10th and 20th each month. This is because when we humans don’t remember the exact number we tend to pick nice numbers (like 1, 10 and 20). This implies that the correct date is not always reported.

Network analysis and network measures are suggested as tools to estimate risk for disease spread in transport systems and risk of disease introduction to individual holdings. Network generation algorithms can be used together with epidemic models to test the ability of network measures to predict disease risks. I have developed, and improved, a network generation algorithm that generates a large variety of structures.

In my thesis I also suggest a method, the good choice heuristic, for generating non-optimal routes. Today coordination of animal transports is neither optimal nor random. In epidemic simulations we need to model routes as close to the actual driven routes as possible and the good choice heuristic can model that. The heuristic is tuned by two parameters and creates coordination of routes from completely random to almost as good as the Clarke and Wright heuristic. I also used the method to make the rough estimate that transport distances for cattle can be reduced by 2-24% with route-coordination optimization of transports-to-slaughter.

Different optimization methods can be used to minimize the transport times for animal-transports in Sweden. For transports-to-slaughter the strategic planning of “which animals to send where” is the first step to optimize. I investigated data from 2008 and found that with strategic planning, given the slaughterhouse capacity, transport distances can be decreased by about 25% for pigs and 40% for cattle. The slaughterhouse capacity and placement are limiting the possibility to minimize transport times for the animals. The transport distances could be decreased by 60% if all animals were sent to the closest slaughterhouse 2008. Small-scale and mobile slaughterhouses have small effect on total transport work (total transport distance for all the animals) but are important for the transport distances of the animals that travel the longest.

 

 

Place, publisher, year, edition, pages
Linköping University , 2012. , 46 p.
Series
Linköping Studies in Science and Technology, Dissertation, ISSN 0345-7524 ; 1434
National Category
Biological Sciences
Research subject
Natural sciences
Identifiers
URN: urn:nbn:se:his:diva-6492ISBN: 978-91-7519-939-9 OAI: oai:DiVA.org:his-6492DiVA: diva2:559547
Note

I Håkansson, N., Henningsson, M., Rönnqvist, M. & Wennergren U., June 2007 Route planning reduces the costs of animal transportation: Animal welfare versus economics. pp. 1044–048. Tartu, Estonia: XIII Int. Congr. Animal hygiene.

II Nöremark, M., Håkansson, N., Lindström, T., Wennergren, U. & Sternberg Lewerin, S., 2009 Spatial and temporal investigations of reported movements, births and deaths of cattle and pigs in Sweden. Acta Veterinaria Scandinavica 51(37).

III Nöremark, M., Håkansson, N., Sternberg Lewerin, S., Lindberg, A. & Jonsson, A., 2011 Network analysis of cattle and pig movements in Sweden: Measures relevant for disease control and risk based surveillance. Preventive Veterinary Medicine 99, pp 78 –90.

IV Håkansson, N., Jonsson, A., Lennartsson, J., Lindström, T. &Wennergren, U., 2010 Generating structure specific networks. Advances in Complex Systems (ACS) 13(02), pp 239–50.

V Lennartsson, J., Håkansson, N.,Wennergren, U. & Jonsson, A., 2012 SpecNet: a spatial network algorithm that generates a wide range of specific structures.(submitted manuscript 1).

VI Håkansson, N., Flisberg, P., Algers, B., Rönnqvist, M. & Wennergren, U., 2012 A strategic analysis of slaughterhouses and animal transportation in Sweden. (manuscript).

Available from: 2012-10-10 Created: 2012-10-09 Last updated: 2013-03-26Bibliographically approved
List of papers
1. Generating Structure Specific Networks
Open this publication in new window or tab >>Generating Structure Specific Networks
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2010 (English)In: Advances in Complex Systems, ISSN 0219-5259, Vol. 13, no 2, 239-250 p.Article in journal (Refereed) Published
Abstract [en]

Theoretical exploration of network structure significance requires a range of different networks for comparison. Here, we present a new method to construct networks in a spatial setting that uses spectral methods in combination with a probability distribu-tion function. Nearly all previous algorithms for network construction have assumed randomized distribution of links or a distribution dependent on the degree of the nodes.We relax those assumptions. Our algorithm is capable of creating spectral networks along a gradient from random to highly clustered or diverse networks. Number of nodes and link density are specified from start and the structure is tuned by three parameters (γ, σ, κ). The structure is measured by fragmentation, degree assortativity, clusteringand group betweenness of the networks. The parameter γ regulates the aggregation in the spatial node pattern and σ and κ regulates the probability of link forming.

Place, publisher, year, edition, pages
World Scientific Publishing Company, 2010
National Category
Natural Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-4500 (URN)10.1142/S0219525910002517 (DOI)000279727100006 ()2-s2.0-77952269152 (Scopus ID)
Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2017-06-16Bibliographically approved
2. SpecNet: A Spatial Network Algorithm that Generates a Wide Range of Specific Structures
Open this publication in new window or tab >>SpecNet: A Spatial Network Algorithm that Generates a Wide Range of Specific Structures
2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 8, e42679Article in journal (Refereed) Published
Abstract [en]

Network measures are used to predict the behavior of different systems. To be able to investigate how various structures behave and interact we need a wide range of theoretical networks to explore. Both spatial and non-spatial methods exist for generating networks but they are limited in the ability of producing wide range of network structures. We extend an earlier version of a spatial spectral network algorithm to generate a large variety of networks across almost all the theoretical spectra of the following network measures: average clustering coefficient, degree assortativity, fragmentation index, and mean degree. We compare this extended spatial spectral network-generating algorithm with a non-spatial algorithm regarding their ability to create networks with different structures and network measures. The spatial spectral networkgenerating algorithm can generate networks over a much broader scale than the non-spatial and other known network algorithms. To exemplify the ability to regenerate real networks, we regenerate networks with structures similar to two real Swedish swine transport networks. Results show that the spatial algorithm is an appropriate model with correlation coefficients at 0.99. This novel algorithm can even create negative assortativity and managed to achieve assortativity values that spans over almost the entire theoretical range.

Place, publisher, year, edition, pages
PLOS, 2012
National Category
Biological Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-6472 (URN)10.1371/journal.pone.0042679 (DOI)000307184700057 ()22876329 (PubMedID)2-s2.0-84864492191 (Scopus ID)
Available from: 2012-10-08 Created: 2012-10-08 Last updated: 2017-06-16Bibliographically approved
3. Spatial and temporal investigations of reported movements, births and deaths of cattle and pigs in Sweden
Open this publication in new window or tab >>Spatial and temporal investigations of reported movements, births and deaths of cattle and pigs in Sweden
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2009 (English)In: Acta Veterinaria Scandinavica, ISSN 1751-0147, E-ISSN 1751-0147, Vol. 51, 37Article in journal (Refereed) Published
Abstract [en]

Background: Livestock movements can affect the spread and control of contagious diseases and new data recording systems enable analysis of these movements. The results can be used for contingency planning, modelling of disease spread and design of disease control programs.

Methods: Data on the Swedish cattle and pig populations during the period July 2005 until June 2006 were obtained from databases held by the Swedish Board of Agriculture. Movements of cattle and pigs were investigated from geographical and temporal perspectives, births and deaths of cattle were investigated from a temporal perspective and the geographical distribution of holdings was also investigated.

Results: Most movements of cattle and pigs were to holdings within 100 km, but movements up to 1200 km occurred. Consequently, the majority of movements occurred within the same county or to adjacent counties. Approximately 54% of the cattle holdings and 45% of the pig holdings did not purchase any live animals. Seasonal variations in births and deaths of cattle were identified, with peaks in spring. Cattle movements peaked in spring and autumn. The maximum number of holdings within a 3 km radius of one holding was 45 for cattle and 23 for pigs, with large variations among counties. Missing data and reporting bias (digit preference) were detected in the data.

Conclusion: The databases are valuable tools in contact tracing. However since movements can be reported up to a week after the event and some data are missing they cannot replace other methods in the acute phase of an outbreak. We identified long distance transports of cattle and pigs, and these findings support an implementation of a total standstill in the country in the case of an outbreak of foot-and-mouth disease. The databases contain valuable information and improvements in data quality would make them even more useful.

Place, publisher, year, edition, pages
BioMed Central, 2009
National Category
Natural Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-4321 (URN)10.1186/1751-0147-51-37 (DOI)000271060700001 ()19811628 (PubMedID)2-s2.0-70449701981 (Scopus ID)
Available from: 2010-08-25 Created: 2010-08-25 Last updated: 2016-05-13Bibliographically approved
4. Network analysis of cattle and pig movements in Sweden: Measures relevant for disease control and risk based surveillance
Open this publication in new window or tab >>Network analysis of cattle and pig movements in Sweden: Measures relevant for disease control and risk based surveillance
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2011 (English)In: Preventive Veterinary Medicine, ISSN 0167-5877, E-ISSN 1873-1716, Vol. 99, no 2-4, 78-90 p.Article in journal (Refereed) Published
Abstract [en]

Registration ofcattle and pigmovements is mandatory in Sweden and all registered movements between farms in the years 2006–2008 were investigated using network analysis. The networks were analysed as monthly and yearly networks, separately per species and with the two species together. Measures that have been previously discussed in relation to outbreaks and disease control were calculated; moreover a measure of the ingoing infection chain was constructed.The ingoing infection chain captures in going contacts through other holdings, taking the temporal aspect and sequence of the movements into account. The distribution of the contacts among the holdings was skewed.Many farms had few or no contacts, while others had many, a pattern which has also been described from other countries. The cattle network and the combined network showed a recurring seasonal pattern, while this was not seen in the pig network.The in-degree was not equivalent to the ingoing infection chain; there were holdings with limited direct contacts, but a large number of indirect contacts.The ingoing infection chain could be a useful measure when setting up strategies for disease control and for risk based surveillance as it identifies holdings with many contacts through live animal movements and thus at potentially higher risk for introduction of contagious diseases.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Cattle-transport, Control strategies, Decision support systems, Epidemics, Eradication programs, Modelling, Seasonal dynamics, Network analysis
National Category
Natural Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-5155 (URN)10.1016/j.prevetmed.2010.12.009 (DOI)000290186100002 ()21288583 (PubMedID)2-s2.0-79953271718 (Scopus ID)
Available from: 2011-06-28 Created: 2011-06-28 Last updated: 2017-06-16Bibliographically approved

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