Caractériser les déterminants physiologiques et génétiques de l’efficience alimentaire des bovins allaitants : le programme BEEFALIM 2020

Dans le contexte actuel de forts coûts des intrants alimentaires et d’impact des productions bovines sur le changement climatique, l’efficience alimentaire apparaît comme un levier d’action pour la durabilité économique et environnementale de l’élevage allaitant. De plus, la valorisation par les bovins d’aliments cellulosiques, non éligibles à l’alimentation humaine et favorisant un maintien des prairies et des services environnementaux associés, représente également un enjeu majeur, en particulier dans les régimes d’engraissement des jeunes bovins. Dans l’objectif d’étudier les déterminants, aussi bien physiologiques que génétiques, de l’efficience alimentaire des bovins allaitants tout en prenant en compte le fait que la filière allaitante repose sur différents types d’animaux (jeunes bovins à l’engraissement mais également mères allaitantes et génisses de renouvellement) et différents types d’alimentation, un vaste programme de recherche a été mené. Intitulé BEEFALIM 2020, celui-ci s’est étalé entre 2013 et 2021 et a permis la production de nombreuses connaissances scientifiques. Cet article introductif présente la structure et les objectifs de BEEFALIM 2020, décrit les dispositifs expérimentaux utilisés et reprend les principaux enseignements du programme en préambule aux trois articles scientifiques qui en rapportent les résultats dans le détail

Wood specific gravity variations within tree trunk: the case study of Legumes representatives in French Guiana

International audienceOver the past decade, much attention has been devoted to the development of forest biomass estimation methods at a stand scale, leading to the establishment of allometric models (Chave et al., 2014). These allometric equations use a unique wood specific gravity value (WSG) per species, but neglect the within tree variations of WSG found by others (Wiemann & Williamson, 1989).The main objectives of this study are (1) to illustrate the diversity of radial (from pith to bark) and longitudinal (from bottom to top) patterns of WSG variation within and between species, (2) to highlight different trends of WSG radial variations and the possible misinterpretations of these trends due to the effect of heartwood and (3) to link these variations and patterns to the successional status of the species (from pioneer to sciaphilic species).We sampled 33 small trees (10<DBH<15cm) at the Paracou field station in French Guiana, belonging to 14 Legumes species, and to different ecological groups according to light. WSG radial profiles were measured at 3 heights along the trunk, and 2 heights along the crown, of each tree.We observed different radial and longitudinal patterns of WSG variation. Pioneer and heliophilic species show both radial and longitudinal increases in WSG, while shade-tolerant and sciaphilic species show the reverse pattern. Hemi-tolerant species show an intermediate pattern, with WSG increasing radially, but decreasing or increasing longitudinally. Decreasing radial pattern in sciaphilic species is due to the presence of heartwood relatively denser than sapwood. When a corrected WSG is used, sciaphilic species show the same radial pattern as hemi-tolerant species (i.e. increasing) or no radial pattern (i.e. ‘flat’ from pith to bark).Decreasing WSG from bottom to top is a general case, excepted for species with low WSG (i.e pioneers). All studied species tend to the same range of WSG values with height (~ 0.6-0.9), supported by a higher WSG under bark within trunk.We also developed a biomass model, implemented under Xplo software (Griffon et al., 2011) to infer trunk biomass from WSG profiles, allowing comparisons of both single- and varying-WSG models.Wood specific gravity variations within tree trunk: the case study of Legumes representatives in French Guiana

Xtrawood: refining estimation of tree above ground biomass using wood density variations and tree structure

International audienceBackgroundTree above ground biomass (AGB) is currently estimated by tree-level allometrical models that take into account, tree volume estimated from proxy variables of tree size (DBH) and species average wood specific gravity (WSG). These methods are common and realistic from a practical point of view. However, they do not take into account deviance from fixed allometrical trajectories and species or tree level WSG variations. Here, we present Xtrawood software that allows computation of tree AGB according to structure and WSG variations.MethodXtrawood reconstructs tree structure and integrates WSG variations by merging tree structure and WSG data measured at different position in trees, leading to the computation of global AGB and visualization of WSG variation along tree structure. Tree structure is measured according to stem dimensions (length, diameter) and positions within tree, and encoded in Multiscale Tree Graph format (MTG). WSG data is made of radial WSG profiles (1 measure each 0,5 cm from pith to bark) sampled at different heights within whole tree. Xtrawood output are illustrated using a dataset collected on an Amazonian forest ‘biomass dominant species’, Dicorynia guianensis Amsh., also known to exhibit substantial WSG gradients along both radial and vertical axis. 9 trees ranging from 15 to 60 cm DBH were measured by climbers. Each tree was felled and samples were collected at different positions (3 in trunk, 1 to 5 in crown) to record WSG radial profiles.ResultsXtrawood allows computation of tree volume, but also visualization of WSG variations in tree as well as inference of WSG radial profiles at different heights. Output variables are decomposed according to different tree scale and locations (axis, trunk/crown) and easy to extract. Xtrawood results will be compared to those of standard estimation method and can be used to identify positions in trees where WSG value leads to the better estimate of tree AGB.Conclusion/perspectiveXtrawood produces AGB estimate with data from intensive measurements practices. The sampling protocol, used here, remains destructive and time-consuming because Xtrawood is not directly dedicated to forest managers, but to help calibration of realistic sampling strategies. Moreover, Xtrawood offers a way to understand relationships between tree development, WSG variations within tree structure and biomass accumulation in the context of natural forests or plantations. A software demo is available at coffee break

Performance evaluation of unified medical language system®'s synonyms expansion to query PubMed

<p>Abstract</p> <p>Background</p> <p>PubMed is the main access to medical literature on the Internet. In order to enhance the performance of its information retrieval tools, primarily non-indexed citations, the authors propose a method: expanding users' queries using Unified Medical Language System' (UMLS) synonyms i.e. all the terms gathered under one unique Concept Unique Identifier.</p> <p>Methods</p> <p>This method was evaluated using queries constructed to emphasize the differences between this new method and the current PubMed automatic term mapping. Four experts assessed citation relevance.</p> <p>Results</p> <p>Using UMLS, we were able to retrieve new citations in 45.5% of queries, which implies a small increase in recall. The new strategy led to a heterogeneous 23.7% mean increase in non-indexed citation retrieved. Of these, 82% have been published less than 4 months earlier. The overall mean precision was 48.4% but differed according to the evaluators, ranging from 36.7% to 88.1% (Inter rater agreement was poor: kappa = 0.34).</p> <p>Conclusions</p> <p>This study highlights the need for specific search tools for each type of user and use-cases. The proposed strategy may be useful to retrieve recent scientific advancement.</p