Vaccination is a suitable tool in the control of Aujeszky's disease outbreaks in pigs using a Population Dynamics P systems model

Aujeszky's disease is one of the main pig viral diseases and results in considerable economic losses in the pork production industry. The disease can be controlled using preventive measures such as improved stock management and vaccination throughout the pig-rearing period. We developed a stochastic model based on Population Dynamics P systems (PDP) models for a standard pig production system to differentiate between the effects of pig farm management regimes and vaccination strategies on the control of Aujeszky's disease under several different epidemiological scenarios. Our results suggest that after confirming the diagnosis, early vaccination of most of the population (>75%) is critical to decrease the spread of the virus and minimize its impact on pig productivity. The direct economic cost of an outbreak of Aujeszky's disease can be extremely high on a previously uninfected farm (from 352-792 Euros/sow/year) and highlights the positive benefits of investing in vaccination measures to control infections. We demonstrate the usefulness of computational models as tools in the evaluation of preventive medicine programs aimed at limiting the impact of disease on animal production.This work was partially supported by FEDER project COMRDI16-1-0035-03

Evaluation of a pig femoral head osteonecrosis model

Background A major cause of osteonecrosis of the femoral head is interruption of a blood supply to the proximal femur. In order to evaluate blood circulation and pathogenetic alterations, a pig femoral head osteonecrosis model was examined to address whether ligature of the femoral neck (vasculature deprivation) induces a reduction of blood circulation in the femoral head, and whether transphyseal vessels exist for communications between the epiphysis and the metaphysis. We also tested the hypothesis that the vessels surrounding the femoral neck and the ligamentum teres represent the primary source of blood flow to the femoral head. Methods Avascular osteonecrosis of the femoral head was induced in Yorkshire pigs by transecting the ligamentum teres and placing two ligatures around the femoral neck. After heparinized saline infusion and microfil perfusion via the abdominal aorta, blood circulation in the femoral head was evaluated by optical and CT imaging. Results An angiogram of the microfil casted sample allowed identification of the major blood vessels to the proximal femur including the iliac, common femoral, superficial femoral, deep femoral and circumflex arteries. Optical imaging in the femoral neck showed that a microfil stained vessel network was visible in control sections but less noticeable in necrotic sections. CT images showed a lack of microfil staining in the epiphysis. Furthermore, no transphyseal vessels were observed to link the epiphysis to the metaphysis. Conclusion Optical and CT imaging analyses revealed that in this present pig model the ligatures around the femoral neck were the primary cause of induction of avascular osteonecrosis. Since the vessels surrounding the femoral neck are comprised of the branches of the medial and the lateral femoral circumflex vessels, together with the extracapsular arterial ring and the lateral epiphyseal arteries, augmentation of blood circulation in those arteries will improve pathogenetic alterations in the necrotic femoral head. Our pig model can be used for further femoral head osteonecrosis studies

Modelling the Spatial Structure of Pig Production in Denmark

In Denmark, the concentration of pig production is highest in the western part of the country. However, there may be even larger local differences in the number of pigs produced. In this study we analyze the determinants of the location of pig production in Denmark with particular focus on spatial externalities and the interaction between the location of pig production and upstream sector and slaughterhouses. It is the assumption that the location of slaughterhouses is influenced by the location of the primary producers, implying that this variable is endogenous, whereas the location of primary producers is independent of the location of slaughterhouses. This is due to the fact that transportation costs of pigs are paid by the cooperatives owning the slaughterhouses. This assumption is tested applying a spatial econometric model. The model is estimated for 1999 and 2004. Furthermore, the impact of negative environmental externalities of pig production on location is analyzed. The results show that spatial externalities have a positive effect on the location of pig production whereas environmental regulation has a negative effect on location.Agglomeration, Externalities, Spatial Econometrics, Polluted Production, Livestock Production/Industries,

THE IMPACT OF MANURE PRODUCTION RIGHTS ON CAPITAL INVESTMENT IN THE DUTCH PIG SECTOR

In this paper the effect of manure production rights on investment decisions of Dutch pig farmers is examined. A dynamic optimization model of investment that explicitly takes zero investments into account is augmented by a constraint on production arising from the introduction of manure production rights. In the theoretical model it is shown that such a constraint has a reducing effect on investment. The presence of this constraint is tested for using GMM structural break tests. The results provide evidence for the hypothesis that manure production rights have reduced investments through its effect on production.Investment, manure production rights, Euler equation, GMM, structural break testing, panel data, pig farms, Livestock Production/Industries,

The Pig Farm Manager for Modelling Pig Production Systems

Before setting up or changing a pig farm operation, the consequences of the farm set up must be explored and changes planned. To calculate technical and economic consequences a farm manager model for pig production systems, the Pig Farm Manager, has been developed. The Pig Farm Manager estimates the effects of various farm designs as well as farm management on production, environmental and economical parameters. The Pig Farm Manager includes simulations for sow farms and finisher pig farms. In the model the user enters farm data on e.g. farm size, housing system or farm management (e.g. feeding strategy), which the model uses to calculate output-parameters. The Pig Farm Manager estimates cost price, profits, gross margins, costs and income per farm, per sow or finisher place. To evaluate the analytical capacities of the model a comparison between a standard sow farm and a high-health-status farm was made. The high-health-farm (HHF) had better growth of piglets, lower mortality rate and better fertility traits for sows compared to a standard farm. However, the HHF had higher investment costs and required more labour. Overall, on the HHF, cost price per piglet was 3.19 lower and yearly farm income about 21,000,- higher compared to the standard sow farm.Livestock Production/Industries,

Correction of Measurement Error in Monthly USDA Pig Crop: Generating Alternative Data Series

The imputed pig death loss contained in the reported monthly U.S. Department of Agriculture (USDA) pig crop data over the December 1995–June 2006 period ranged from 24.93% to 12.75%. Clearly, there are substantial measurement errors in the USDA monthly pig crop data. In this paper, we present alternative monthly U.S. pig crop data using the biological production process, which is compatible with prior knowledge of the U.S. hog industry. Alternative pig crop data are applied to a slaughter hog model and tested comparatively to USDA pig crop. Test results reject the validity of USDA pig crop data in favor of the alternative data.biological production process, measurement error, monthly USDA pig crop data, pig death loss, Agribusiness, Farm Management, Livestock Production/Industries, Q11, Q13, C12,

Porcine reproductive and respiratory syndrome virus (PRRSV) in GB pig herds : farm characteristics associated with heterogeneity in seroprevalence

Background: The between- and within-herd variability of porcine reproductive and respiratory syndrome virus (PRRSV) antibodies were investigated in a cross-sectional study of 103 British pig herds conducted 2003–2004. Fifty pigs from each farm were tested for anti-PRRSV antibodies using ELISA. A binomial logistic model was used to investigate management risks for farms with and without pigs with PRRSV antibodies and multilevel statistical models were used to investigate variability in pigs' log ELISA IRPC (relative index × 100) in positive herds. Results: Thirty-five herds (34.0%) were seronegative, 41 (39.8%) were seropositive and 27 (26.2%) were vaccinated. Herds were more likely to be seronegative if they had < 250 sows (OR 3.86 (95% CI 1.46, 10.19)) and if the nearest pig herd was ≥ 2 miles away (OR 3.42 (95% CI 1.29, 9.12)). The mean log IRPC in seropositive herds was 3.02 (range, 0.83 – 5.58). Sixteen seropositive herds had only seropositive adult pigs. In these herds, pigs had -0.06 (95% CI -0.10, -0.01) lower log IRPC for every mile increase in distance to the nearest pig unit, and -0.56 (95% CI -1.02, -0.10) lower log IRPC when quarantine facilities were present. For 25 herds with seropositive young stock and adults, lower log IRPC were associated with isolating purchased stock for ≥ 6 days (coefficient - 0.46, 95% CI -0.81, -0.11), requesting ≥ 48 hours 'pig-free time' from humans (coefficient -0.44, 95% CI -0.79, -0.10) and purchasing gilts (coefficient -0.61, 95% CI -0.92, -0.29). Conclusion: These patterns are consistent with PRRSV failing to persist indefinitely on some infected farms, with fadeout more likely in smaller herds with little/no reintroduction of infectious stock. Persistence of infection may be associated with large herds in pig-dense regions with repeated reintroduction

Experimental pig-to-pig transmission dynamics for African swine fever virus, Georgia 2007/1 strain

African swine fever virus (ASFV) continues to cause outbreaks in domestic pigs and wild boar in Eastern European countries. To gain insights into its transmission dynamics, we estimated the pig-to-pig basic reproduction number (R 0) for the Georgia 2007/1 ASFV strain using a stochastic susceptible-exposed-infectious-recovered (SEIR) model with parameters estimated from transmission experiments. Models showed that R 0 is 2·8 [95% confidence interval (CI) 1·3–4·8] within a pen and 1·4 (95% CI 0·6–2·4) between pens. The results furthermore suggest that ASFV genome detection in oronasal samples is an effective diagnostic tool for early detection of infection. This study provides quantitative information on transmission parameters for ASFV in domestic pigs, which are required to more effectively assess the potential impact of strategies for the control of between-farm epidemic spread in European countries.ISSN:0950-2688ISSN:1469-440

Modelling animal farming systems as supply chains

Traditionally considered as autonomous entities, farms are actually parts of complex supply chains. Addressing sustainability issues needs to account for this reality. My contribution will depict a modelling approach of the pig industry in the Reunion Island representing the pig production chain from the raw feedstuff suppliers to the pig products retailers, passing by the rearing enterprises. This model aims at simulating both the material flows and coordination among the stakeholders. It is based on a modelling ontology where human action is explicitly represented. (Texte intégral