Prediction of pig trade movements in different European production systems with exponential random graph models

In most European countries, data regarding movements of live animals are routinely collected and can greatly aid predictive epidemic modeling. However, the use of complete movements' dataset to conduct policy-relevant predictions has been so far limited by the massive amount of data that have to be processed (e.g., in intensive commercial systems) or the restricted availability of timely and updated records on animal movements (e.g., in areas where small-scale or extensive production is predominant). The aim of this study was to use exponential random graph models (ERGMs) to reproduce, understand, and predict pig trade networks in different European production systems. Three trade networks were built by aggregating movements of pig batches among premises (farms and trade operators) over 2011 in Bulgaria, Extremadura (Spain), and Côtes-d'Armor (France), where small-scale, extensive, and intensive pig production are predominant, respectively. Three ERGMs were fitted to each network with various demographic and geographic attributes of the nodes as well as six internal network configurations. Several statistical and graphical diagnostic methods were applied to assess the goodness of fit of the models. For all systems, both exogenous (attribute-based) and endogenous (network-based) processes appeared to govern the structure of pig trade network, and neither alone were capable of capturing all aspects of the network structure. Geographic mixing patterns strongly structured pig trade organization in the small-scale production system, whereas belonging to the same company or keeping pigs in the same housing system appeared to be key drivers of pig trade, in intensive and extensive production systems, respectively. Heterogeneous mixing between types of production also explained a part of network structure, whichever production system considered. Limited information is thus needed to capture most of the global structure of pig trade networks. Such findings will be useful to simplify trade networks analysis and better inform European policy makers on risk-based and more cost-effective prevention and control against swine diseases such as African swine fever, classical swine fever, or porcine reproductive and respiratory syndrome

Questionnaire-based assessment of wild boar/domestic pig interactions and implications for disease risk management in Corsica

Wild boars and domestic pigs belong to the same species (Sus scrofa). When sympatric populations of wild boars, feral pigs, and domestic pigs share the same environment, interactions between domestic and wild suids (IDWS) are suspected to facilitate the spread and maintenance of several pig pathogens which can impact on public health and pig production. However, information on the nature and factors facilitating those IDWS are rarely described in the literature. In order to understand the occurrence, nature, and the factors facilitating IDWS, a total of 85 semi-structured interviews were implemented face to face among 25 strict farmers, 20 strict hunters, and 40 hunting farmers in the main traditional pig-farming regions of Corsica, where IDWS are suspected to be common and widespread. Different forms of IDWS were described: those linked with sexual attraction of wild boars by domestic sows (including sexual interactions and fights between wild and domestic boars) were most frequently reported (by 61 and 44% of the respondents, respectively) in the autumn months and early winter. Foraging around common food or water was equally frequent (reported by 60% of the respondents) but spread all along the year except in winter. Spatially, IDWS were more frequent in higher altitude pastures were pig herds remain unattended during summer and autumn months with limited human presence. Abandonment of carcasses and carcass offal in the forest were equally frequent and efficient form of IDWS reported by 70% of the respondents. Certain traditional practices already implemented by hunters and farmers had the potential to mitigate IDWS in the local context. This study provided quantitative evidence of the nature of different IDWS in the context of extensive commercial outdoor pig farming in Corsica and identified their spatial and temporal trends. The identification of those trends is useful to target suitable times and locations to develop further ecological investigations of IDWS at a finer scale in order to better understand diseases transmission patterns between populations and promote adapted management strategies

Randomised controlled trial to evaluate the effect of foot trimming before and after first calving on subsequent lameness episodes and productivity in dairy heifers

The objective of this study was to assess both independent and combined effects of routine foot trimming of heifers at 3 weeks pre-calving and 100 days post calving on the first lactation lameness and lactation productivity. A total of 419 pre-calving dairy heifers were recruited from one heifer rearing operation over a 10-month period. Heifers were randomly allocated into one of four foot trimming regimens; pre-calving foot trim and post-calving lameness score (Group TL), pre-calving lameness score and post-calving foot trim (Group LT), pre-calving foot trim and post-calving foot trim (Group TT), and pre-calving lameness score and post-calving lameness score (Group LL, control group). All heifers were scored for lameness at 24 biweekly time points for 1 year following calving, and first lactation milk production data were collected. Following calving, 172/419 (41.1%) of heifers became lame during the study (period prevalence), with lameness prevalence at each time-point following calving ranging from 48/392 (12.2%) at 29–42 days post-calving to 4/379 (1.1%) between 295 and 383 days after calving. The effects of the four treatment groups were not significantly different from each other for overall lameness period prevalence, biweekly lameness point prevalence, time to first lameness event, type of foot lesion identified at dry off claw trimming, or the 4% fat corrected 305-day milk yield. However, increased odds lameness was significantly associated with a pre-calving trim alone (P = 0.044) compared to the reference group LL. The odds of heifer lameness were highest between 0 and 6 weeks post-partum, and heifer farm destination was significantly associated with lameness (OR 2.24), suggesting that even at high standard facilities, environment and management systems have more effect on heifer foot health than trimming

Interdigital dermatitis, heel horn erosion, and digital dermatitis in 14 Norwegian dairy herds

AbstractThe aim of this study was to assess infectious foot diseases, including identification and characterization of Dichelobacter nodosus and Treponema spp., in herds having problems with interdigital dermatitis (ID) and heel horn erosion (E) and in control herds expected to have few problems. We also wanted to compare diseased and healthy cows in all herds. The study included 14 dairy herds with a total of 633 cows. Eight herds had a history of ID and E, and 6 were control herds. All cows were scored for lameness, and infectious foot diseases on the hind feet were recorded after trimming. Swabs and biopsies were taken from the skin of 10 cows in each herd for bacterial analyses. In total, samples were taken from 34 cows with ID, 11 with E, 40 with both ID and E, and 8 with digital dermatitis (DD), and from 47 cows with healthy feet. Swabs were analyzed for identification and characterization of D. nodosus by PCR, culture, virulence testing, and serotyping. Biopsies were analyzed by fluorescent in situ hybridization regarding histopathology, identification, and characterization of Treponema spp., and identification of D. nodosus. Interdigital dermatitis was the most frequent foot disease, with a prevalence of 50.4% in problem herds compared with 26.8% in control herds. Heel horn erosion was recorded in 34.8% of the cows in problem herds compared with 22.1% in control herds. Dichelobacter nodosus was detected in 97.1% of the cows with ID, in 36.4% with E, in all cows with both ID and E, in all cows with DD, and in 66.0% of cows with healthy feet. All serogroups of D. nodosus except F and M were detected, and all isolates were defined as benign by the gelatin gel test. Treponema spp. were detected in 50.0% of the cows with ID, in 9.1% with E, in 67.5% with ID and E, in all cows with DD, and in 6.4% of those with healthy feet. In total, 6 previously described phylotypes (PT) of Treponema were detected: PT1, PT3, PT6, PT13, and PT15 in cows with ID, PT1 in a cow with E, and PT1, PT2, PT3, PT6, and PT13 in cows with both ID and E. One new phylotype (PT19) was identified. The epidermal damage score was higher but the difference in inflammatory response of the dermis was minor in cows with ID versus those with healthy feet. Fisher’s exact test revealed an association between ID and D. nodosus, and between ID and Treponema spp. Logistic regression revealed an association between both ID and E and dirty claws (odds ratios=1.9 and 2.0, respectively). Our study indicates that D. nodosus, Treponema spp., and hygiene are involved in the pathogenesis of ID

Evaluation des mesures de maîtrise de la dermatite digitée dans les troupeaux bovins laitiers

The aim of this PhD thesis was to assess the effectiveness of different promising measures to durably decrease the prevalence of digital dermatitis (DD) in dairy herds. The treatment modalities to be studied should be acceptable for farmers and not toxic both for Human and the Environment. A first part was dedicated to investigate the motivations and limits of French dairy farmers towards the implementation of different treatments against DD. The need for evidence of optimal frequency of application of collective treatments with footbath or another way of application was enlighten. After the development and the assessment of a simple method for scoring of DD lesions in the milking parlor, a clinical trial was conducted in 52 dairy herds. This clinical trial aimed at assessing, using survival analysis, the relative effectiveness of 4 different treatment regimens and herd practices to decrease the incidence and increase the cure rate of DD lesion. The implementation of walk-through footbath and collective spraying using a solution of chelated minerals were effective to significantly decrease the incidence and improve cure rate of DD lesions when applied over 2 days every fortnight. Legs hygiene and hoof trimming before DD detection were also found crucial to control DD. Lastly, the impact of DD on milk yield was estimated to 0,6 to 0,9 kg/day. These results highlight the need of combining several control measures, including both treatments and herd practices to design relevant control strategies of DD in dairy herds.L’objectif de cette thèse était d’évaluer des mesures jugées prometteuses pour diminuer durablement la prévalence de la dermatite digitée (DD) dans les troupeaux bovins laitiers. Les pratiques de traitement devaient être efficaces, acceptables pour les éleveurs et non toxiques pour l’Homme et l’Environnement. Une première partie s’est intéressée aux freins et motivations des éleveurs français vis-à-vis des pratiques de traitement de la DD. Il en ressortait le besoin d’identifier des régimes optimaux d’application des traitements, tout en étudiant des alternatives au pédiluve pour l’application de traitements collectifs. Après avoir mis au point et évalué une méthode simple de notation de la DD en salle de traite, un essai clinique a été mené dans 52 troupeaux bovins laitiers. Cet essai a permis d’évaluer, à l’aide d’analyses de survie, l’efficacité relative de 4 protocoles de traitement et des pratiques d’élevage pour diminuer l’incidence et améliorer la guérison des lésions de DD. Il a été montré qu’un traitement à base de minéraux chélatés appliqué 2 jours toutes les 2 semaines, via un pédiluve de passage ou une application par spray ensalle de traite est efficace pour diminuer l’incidence et améliorer la guérison clinique des lésions de DD. La propreté des pieds et la réalisation d’un parage avant la détection d’une lésion de DD jouaient également un rôle essentiel. Enfin, l’impact de la DD sur la production laitière a pu être estimé à 0,6 à 0,9 kg/jour. Les résultats de cette thèse renforcent la nécessité d’une approche globale qui intègre des protocoles de traitement et les pratiques d’élevage pour élaborer des stratégies de contrôle de la DD efficaces et rentable

Multiparametric strategy for robust design in fatigue

La conception robuste de pièce mécaniques consiste à prendre en compte dans la modélisation les sources d'incertitudes.Le modèle devient alors assez représentatif de la réalité pour pouvoir diminuer les marges de sécurité, qui permettent de garantir que la pièce en fonctionnement ne sera pas mise en défaut.Dans le cas de pièces aérospatiales, une diminution des marges de sécurité est un enjeu économique majeur car cela entraîne une diminution du poids des pièces.La probabilité de défaillance est une des quantités critiques lors de la conception robuste. Celle-ci quantifie le risque de défaillance de la pièce en comparant la probabilité de résistance du matériau (caractérisée à partir d'essais sur éprouvettes) avec la probabilité de sollicitation du matériau, qui est déterminée à partir des contraintes extérieures à la pièce et des caractéristiques du matériau. C'est ce dernier problème qui a fait l'objet de cette thèse.Dans le cas d'un comportement non linéaire du matériau, la détermination de la probabilité de sollicitation impose d'exécuter de nombreuses fois un calcul de la pièce pour différentes valeurs des conditions aux limites et des paramètres du comportement matériau.Ceci devient rapidement hors de portée sans une stratégie adaptée, un calcul pouvant prendre jusqu'à 12 heures.Une stratégie dédiée à la résolution de l'ensemble de ces calculs est proposée dans ce travail. Elle tire parti de la similarité des calculs pour diminuer le temps total nécessaire. Un gain allant jusqu'à 30 est atteint sur des pièces industrielles simples en quasi-statique avec un comportement élasto-viscoplastique.The robust design of mechanical parts consists in modeling the sources of uncertainty.The model becomes fairly representative of the reality in order to reduce safety margins, which guarantee that the operating part will not been at fault.In the case of aerospace parts, a reduction of safety margins is a major economic issue as it leads to a decrease in weight.The probability of failure is a critical quantity in the robust design. It quantifies the risk of failure of the part by comparing the likelihood of resistance of the material (characterized from tests on specimens) with the probability of solicitation of the material, which is determined from external constraints to the part and characteristics of the material. This last problem has been the subject of this thesis.In the case of a non-linear behavior of the material, determining the probability of solicitation requires to run many times a calculation of the part for different values of boundary conditions and parameters values of the material constitutive law.This is quickly becoming out of reach without an appropriate strategy, as one calculation can take up to 12 hours.A strategy dedicated to solving all of these calculations is proposed in this work. It takes advantage of the similarity of the calculations to reduce the total time required. A gain of up to 30 is reached on industrial parts with quasi-static elastic-viscoplastic behavior