Instrumented Indentation of Super-Insulating Silica Compacts

International audienceHighly porous silica compacts for superinsulation were characterized by instrumented indentation. Samples showed a multi-scale stacking of silica particles with a total porous fraction of 90 vol %. The two main sources of silica available for the superinsulation market were considered: fumed silica and precipitated silica. The compacts processed with these two silica displayed different mechanical properties at a similar porosity fraction, thus leading to different usage properties, as the superinsulation market requires sufficient mechanical properties at the lowest density. The measurement of Young's modulus and hardness was possible with spherical indentation, which is an efficient method for characterizing highly porous structures. Comparison of the mechanical parameters measured on silica compacts and silica aerogels available from the literature was made. Differences in mechanical properties between fumed and precipitated compacts were explained by structural organization

La place de l’élevage laitier dans la bioéconomie circulaire

La place de l’élevage laitier dans la bioéconomie circulaire. Colloque Apivale - Produits résiduaires organiques : ingrédients clés de la bioéconomie circulair

Thermal preference plasticity of Drosophila suzukii: a key to its invasion success?

National audienceTemperature is one of the most important abiotic factors affecting the physiology of ectotherms. Small ectotherms like insects rely on behavioral thermoregulation to maintain their body temperature within permissive range. The plasticity of preferred body temperature (Tp) contributes to an organism’s adaptive capacity to environmental changes. It also plays a substantial role in the establishment of invasive species. Here we studied the Tp plasticity of a major pest, the fruit fly Drosophila suzukii. A high Tp plasticity allows for more precise behavioral thermoregulation, decreasing the selection pressure on thermal tolerance. We hypothesized that larvae are less plastic than adult because they are constrained by the fruit selected by the mother. Furthermore, we tested whether the endosymbiont Wolbachia played a role in the level of plasticity of Tp.We measured the response of Tp to developmental temperature using a thermal gradient apparatus in a controlled laboratory environment. We assessed the effect of variables such as developmental stage, age, sex, reproductive status, and the presence of Wolbachia (developmental plasticity). We followed the flies for several generations to question a transgenerational effect on Tp.All studied variables affected D. suzukii’s Tp, suggesting a high plasticity. The developmental temperature influenced the mean Tp of adults, but not larvae, highlighting the importance of the mother’s temperature choice for its progeny. Females preferred higher temperatures than males, maybe to accelerate egg maturation. Wolbachia infected individuals had lower Tp than uninfected flies. The high plasticity of D. suzukii’s Tp could have contributed to its invasion success worldwide

Nitrogen management in french dairy syst ems: evaluation and enhancement of nitro gen efficiency and econo mic performance

National audienceWhile nitrogen (N) management has improved significantly on livestock farms, with positive consequences for nitrate concentrations in surface waters (Manneville et al., 2017), the French dairy farming sector must continue its efforts. At the same time, dairy farmers have to cope with market developments (increased milk demand), price volatility and changing agricultural policies. Therefore, reconciling respect for the environment and economic competitiveness has become one of their main objectives. To support them, the “Inosys-Réseau d’Elevage” farms network associates 2,000 breeders and 240 engineers to analyze the management of the farms and disseminate the knowledge and tools needed to improve the systems. The analysis of these farms’ data aims to identify sustainable production systems and key actions that can be implemented by farmers to improve nitrogen (and phosphorus) management, related to economic performances (full results in Foray et al., 2017)

Invasive success of Drosophila suzukii: Is Wolbachia playing a role?

International audienceInvasive species constitute a worldwide issue, jeopardizing biodiversity and engendering important economic losses. A better understanding of how they can establish under envi- ronmental conditions that are different from those they encounter in their native range is necessary. Drosophila suzukii is an invasive pest worldwide, originating from Asia. Because of its impressive abilities to develop in new environments, it became a precious model or- ganism to understand invasive success. Among the traits that may have contributed to its success are (1) a highly polyphagous diet allowing the fly to develop within several fruits species all year round; and (2) the female’s ability to lay eggs in healthy fruits, a niche ne- glected by other Drosophilidae. Moreover, D. suzukii hosts the Wolbachia strain wSuz, the role of which is still under study. Hypotheses include towards a mutualistic role. We con- ducted experiments to better understand how Wolbachia affects D. suzukii fitness, thermal biology and metabolism. In stressful conditions (e.g., fluctuant thermal regime, diet change), flies infected with Wolbachia had a higher survival, a lower thermal preference and a lower metabolic rate. This presentation questions wether wSuz played a role in D. suzukii invasive success, specifically linked with its polyphagy and thermal preference

Thermal preference plasticity of a major pest: a key to its invasion success?

Temperature is one of the most important abiotic factors affecting the physiology of ectotherms. Small ectotherms like insects rely on behavioral thermoregulation to maintain their body temperature within permissive range. The plasticity of preferred body temperature (Tp) contributes to an organism’s adaptive capacity to environmental changes. It also plays a substantial role in the establishment of invasive species. Here we studied the Tp plasticity of a major pest, the fruit fly Drosophila suzukii. A high Tp plasticity allows for more precise behavioral thermoregulation, decreasing the selection pressure on thermal tolerance. We hypothesized that larvae are less plastic than adult because they are constrained by the fruit selected by the mother. Furthermore, we tested whether the endosymbiont Wolbachia played a role in the level of plasticity of Tp.We measured the response of Tp to developmental temperature using a thermal gradient apparatus in a controlled laboratory environment. We assessed the effect of variables such as developmental stage, age, sex, reproductive status, and the presence of Wolbachia (developmental plasticity). We followed the flies for several generations to question a transgenerational effect on Tp.All studied variables affected D. suzukii’s Tp, suggesting a high plasticity. The developmental temperature influenced the mean Tp of adults, but not larvae, highlighting the importance of the mother’s temperature choice for its progeny. Females preferred higher temperatures than males, maybe to accelerate egg maturation. Wolbachia infected individuals had lower Tp than uninfected flies. The high plasticity of D. suzukii’s Tp could have contributed to its invasion success worlwide

Thermal acclimation effect on the metabolic rate of a pest insect

International audienc

In pasture-based dairy systems, breeding and feeding strategies affect GHG emissions and nitrogen losses

International audienceWhich pasture-based dairy system is the most beneficial from an environmental impacts perspective? The results of the long-term experiment ‘Which cow for which system?’ (WCWS) undertaken at the INRAE experimental farm of Le Pin-au-Haras in Normandy were used to address this question. One hundred and sixty dairy systems were designed from the WCWS trial based on six factors monitored in the experiment, including feeding strategy (low (LFS) with only grass or high (HFS) with less grass, maize silage and concentrates) and breed (Holstein or Normande). Their common objective was to produce yearly 420,000 litres of milk. The CAP’2ER tool was used to determine the greenhouse gas (GHG) emission and the nitrogen losses of each system. The average GHG gross emission was 1.18±0.08 kg eqCO2 l-1 of milk and the average nitrogen balance was 146±10 kg N ha-1. The ‘LFS’ systems and the ‘Holstein breed’ systems had lower gross GHG emissions. The LFS had a higher nitrogen surplus (+7 kg N ha-1) but the nitrogen leaching risk was significantly lower than HFS (-27 kg N ha-1). This comparative analysis highlights the need for environmental trade-offs in the face of the diversity of impacts assessed

De l’animal au territoire, regards sur l’efficience de l’azote dans les systèmes bovins laitiers

International audienceImproving the use of nitrogen at all stages of its use is a priority, especially in livestock systems where it remains relatively low. There are many nitrogen use efficiency indicators based on various calculations depending on the context and the scales considered. The literature is full of examples of win-win practices improving its use and reducing its losses to the environment. But few studies present an integrative view of these gains at supra scales. This article first recalls the main strategies for increasing nitrogen use efficiency at the animal, farm and territory levels. The analysis of the integration of gains at global levels shows that improving efficiency at a given scale does not systematically generate an efficiency gain at larger scales or for the whole system. Moreover, the search for high efficiency does not always allow a reduction in nitrogen losses, some of the most efficient systems are also those that generate the highest impacts, a consequence of the high levels of N used. Efficiency indicators remain useful tools for improving nitrogen use in agricultural systems, but should be consistently associated with nitrogen loss indicators to better consider the consequences of agricultural systems on the environment.Améliorer la valorisation de l’azote à toutes les étapes de son utilisation est une priorité, notamment en élevage où elle demeure relativement faible. Les indicateurs d’efficience azotée sont nombreux et basés sur des méthodes de calculs diverses selon le contexte et les échelles considérées. La littérature illustre un certain nombre de pratiques vertueuses, le plus souvent applicables à l’échelle de l’animal ou du troupeau, qui en améliorent la valorisation. Mais peu d’études présentent une vision intégrative de ces gains aux niveaux d’organisation supérieurs comme l’exploitation ou le territoire. Cet article rappelle tout d’abord les principales stratégies qui permettent d’augmenter l’efficience d’utilisation de l’azote à l’échelle de l’animal, de l’exploitation et du territoire. L’analyse de ces gains à différentes échelles met en évidence qu’une amélioration de l’efficience à un niveau donné n’induit pas systématiquement un gain d’efficience à l’étage supérieur ou pour l’ensemble du système. Par ailleurs, la recherche d’une efficience élevée ne garantit pas systématiquement une réduction des pertes azotées vers l’environnement : certains systèmes d’élevage les plus efficients sont aussi ceux qui génèrent le plus d’impacts du fait des quantités importantes d’azote utilisées. Les indicateurs d’efficience s’avèrent des outils utiles pour améliorer l’utilisation de l’azote dans les systèmes agricoles, mais ces ratios ne disent rien des quantités mises en jeu tant au numérateur qu’au dénominateur. Ils devraient donc être systématiquement associés à des indicateurs de pertes azotées pour une meilleure prise en compte des conséquences des systèmes agricoles sur les milieux naturels

La place de l’élevage laitier dans la bioéconomie circulaire

La place de l’élevage laitier dans la bioéconomie circulaire. Colloque Apivale - Produits résiduaires organiques : ingrédients clés de la bioéconomie circulair