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Drought can induce phenotypic plasticity in a range of plant root and shoot traits. These traits have been shown to explain differences in root and shoot litter decomposability between species. However, it is unknown how drought-induced plasticity of root and shoot traits alters their decomposability. To investigate this issue across a range of species, we grew a grass Lolium perenne, a forb Plantago lanceolata and a legume Trifolium repens common to European temperate grasslands and subjected them to a 5-week moderate drought treatment. We compared morphological and chemical root and shoot traits of the droughted plants to well-watered controls. We then conducted a decomposition assay of the senesced root and shoot material over 16 weeks, with mass loss measurements at five timepoints. Drought had significant and sometimes strong effects on morphological and chemical root and shoot traits of all three species, sometimes similar to differences between species and generally in line with a shift to a more resource-conservative strategy. Drought also increased the labile litter fraction in roots of Lolium perenne, which was associated with a substantial increase in non-structural carbohydrates. Drought decreased the labile litter fraction in shoots of Plantago lanceolata, but this could not be explained by the traits we measured. Drought effects on litter decomposability were weaker than on plant traits. Our results suggest that plant trait-mediated effects of drought on litter decomposability can either increase or decrease vegetation feedbacks to climate change. They also show that drought-induced plasticity in root and shoot traits does not automatically translate into equivalent changes in litter decomposability.

International audience; Highlights:• Digestibility of weeds in olive groves and vineyards is comparable to forage species.• CWM of LDMC negatively correlates with weeds forage quality.• Disturbing agricultural practices like tillage increased the digestibility of weeds.• No relationship was found between weeds biomass and leaf traits nor pedoclimatic drivers.• Weeds in olive groves and vineyards represent a promising forage resource for livestock.Abstract:Biodiversity presence in perennial agroecosystems increases the provision of ecosystem services (ES). Weeds are known to deliver supporting or regulating services but their potential to provide provisioning services is less studied. Our study aims to quantify the potential of weeds to provide forage resources for livestock in two Mediterranean perennial agroecosystems: olive groves and vineyards. We used a trait-based approach to investigate the abiotic determinants of weed quality and quantity variations at both the species and community levels. We surveyed spontaneous vegetation in 16 vineyards and 16 olive groves in the French Mediterranean region with contrasting pedoclimatic conditions and agricultural practices, during spring and fall 2021. Four leaf traits were measured: Leaf Dry Matter Content (LDMC), Specific Leaf Area (SLA), Leaf Nitrogen Content (LNC) and leaf C/N ratio (Leaf C/N) and four forage potential indicators: dry matter digestibility (DMD), crude proteins (CP), neutral detergent fiber content (NDF) and aboveground biomass (AB). We found that DMD of perennial agroecosystems weeds is high (689 ± 116 g kg−1), and can be compared to those of forage species. Using linear mixed models and path analysis, we found that, at the community scale, LDMC is negatively linked to weed forage quality and that disturbing agricultural practices like tillage, increase weed forage quality. However we did not find any effect of agricultural practices or pedoclimate on weeds leaf traits or on weeds quantity. Our results revealed the potential of weeds as highly digestible forage resources for livestock. The long-term aim is to promote the integration of livestock in perennial cropping systems in order to reduce the use of herbicides and/or tillage and to diversify agricultural production.

Background and Aims Decomposition is a major ecosystem process which improves soil quality. Despite that, only a few studies have analysed decomposition in an agricultural context, while most agrosystems (e.g. vineyards) are facing decreasing soil quality. The objective of this study is to understand the impacts of both pedoclimate and weed management on the mass loss of vineyard weed communities during the early stages of the decomposition process through their functional properties. Methods In 16 Mediterranean vineyards representing both a pedoclimate and a soil management gradient, we measured the mass loss of green above-ground biomass of 50 weed communities during decomposition in standard conditions and key leaf traits of dominant species [e.g. leaf dry matter content (LDMC) and leaf lignin to nitrogen ratio (lignin:N)]. Both the mean [i.e. community-weighted mean (CWM)] and diversity (i.e. Rao index) were computed at the community level. Path analysis was used to quantify the effects of agro-environmental filters on the mass loss of weed communities through their functional properties. Key Results Tillage and mowing filtered more decomposable communities than chemical weeding (16 and 8 % of higher mass loss after 2 months of decomposition). Path analysis selected weed management practice type as the main factor determining mass loss through its effect on functional properties, while soil and climate had minor and no effects, respectively. Chemical weeding favoured communities with higher investment in resistant leaves (e.g. 38 % higher lignin:N, 22 % lower leaf nitrogen content) which resulted in lower mass loss compared with tilled and mowed communities. Mowing favoured communities with 47 % higher biomass and with 46 % higher nitrogen content. Conclusions Weed management significantly influenced weed mass loss, while the pedoclimate had little effect. Our results suggest that mowing is a promising alternative to herbicide use, favouring higher biomass, nitrogen content and decomposability potential of weeds.

Dans les régions tropicales, où les rations de base sont souvent déficitaires en protéines, la complémentation est cruciale. Des alternatives à l’utilisation de tourteau de soja sont potentiellement disponibles dans les systèmes agroforestiers et les systèmes mixtes polyculture-élevage intégrés, bien que l’offre soit plus importante pour les ruminants que les monogastriques non herbivores. La valeur nutritionnelle des ressources n’est pas la seule règle de décision : l’évaluation des stratégies alimentaires, dans une approche multicritère, doit considérer les différents services productifs et non productifs. Elle doit en outre prendre en compte la compétition possible entre l’utilisation des ressources par l’Homme et l’animal. Dans le cadre des systèmes mixtes polyculture-élevage intégrés, les ressources duales, dont la valorisation intégrale concilie les besoins de l’Homme et de l’animal, occupent une place stratégique : graines et fanes de légumineuses, feuilles et tubercules de manioc ou de patate douce etc. Les légumineuses annuelles, pérennes ou arbustives présentent des atouts agronomiques et environnementaux importants dans les systèmes intégrés par leur capacité à fixer l’azote. Le rôle de recyclage et la faible emprise sur le foncier agricole des nouvelles sources d’aliments (plantes aquatiques, microorganismes, insectes, vers de terre) sont aussi un atout pour leur développement. La mise au point de technologies adaptées pour lever les verrous (facteurs antinutritionnels, conservation…) permettra de valoriser pleinement le potentiel de nombreuses ressources protéiques.

International audience; Native pastures that present high botanical richness produce a variety of feed items for grazing herbivores. Diet selection takes place at the bite scale and, at a daily scale, the sum of bites composing the intake determines diet characteristics. The objective of this paper is to bring an original contribution to the understanding of diet selection in diverse foraging environments such as native Pampa grasslands. The issues are 1) to improve grazing management in Pampa ecosystems and 2) to evaluate the ability of native pastures to feed a herd in order to reduce supplementation and to improve the economic sustainability of extensive systems. We hypothesize that the information contained in the infrared spectra of plant samples corresponding to potential bites can be useful for establishing functional bite categories, which, in turn, can be used to understand and manage pastoral ecosystems. We analyzed the near-infrared spectrum (NIRS) of 1 515 bite samples gathered in 2012 using the continuous bite monitoring method applied to heifers continuously grazing on Pampa grassland at five grazing intensities (randomized block design with two replicates, applied since 1987). On the basis of the main wavelengths, a statistical classification of bite samples was produced and five classes were described: 1) small bites of wetland grasses and short grass; 2) medium bites of forbs and short grass; 3) small bites of short Poaceae and mixed species; 4) large bites on tussocks of Poaceae; and 5) extralarge bites on stiff tussock of Poaceae and Apiaceae. In order to evaluate the functional value of the classification, we tested its ability to take seasonal changes in pasture composition into account and to describe the variations in animal intake and performance in contrasted grazing conditions. We concluded that the NIRS is a good support for establishing functional classes of feed items that can be used to understand the foraging behavior and diet composition of grazing herbivores. Our approach was tested in Pampa grasslands grazed by cattle but should be applicable to a wide range of ecosystems, provided that chemical composition is more relevant for selection than feed item accessibility.

International audience; With the rise of large herbivore populations in most northern hemisphere forests, browsing is becoming an increasingly important driver of forest regeneration dynamics. Among other processes affecting the regeneration, the concept of plant-herbivore feedback loops holds that browsed saplings are more subject to subsequent herbivory. This phenomenon is interpreted as a consequence of compensatory growth following browsing since fast growth is generally associated with higher digestibility and lower defense against herbivores. However, studies linking browsing-induced trait variations to subsequent attractiveness to herbivores are still lacking, especially in the forest context. In this study, we experimentally examine the existence of a feedback loop between oak (Quercus robur L.) and roe deer (Capreolus capreolus) and investigate its underlying morphological and chemical traits. We simulated single and repeated roe deer browsing on nursery-grown oak saplings and measured the changes in sapling height growth, lateral branching, leaf traits and winter shoot traits over two years. We conducted winter feeding trials with tame roe deer one year after the first treatment to test the effect of simulated browsing on sapling attractiveness. Simulated browsing reduced sapling height growth but had no effect on branching. Simulated browsing had no effect on leaf traits after half a year, but decreased the phenolic content and increased the fiber content of winter shoots the following winter. Contrary to our predictions, roe deer preferentially browsed control saplings over saplings previously browsed. After two years, repeated browsing promoted fast carbon acquisition leaf traits (high chlorophyll, high specific leaf area and low fiber content), reduced leaf phenolic content and increased leaf digestibility. We showed that a reduction in 1-year-old oak sapling height growth following browsing, combined with increased structural defense at the expense of chemical defense in winter shoots the following winter, was correlated with reduced browsing pressure, thereby challenging the feedback loop hypothesis. However, we also demonstrated that repeated browsing promoted fast carbon acquisition leaf traits in 2.5-year-old saplings, which tend to support the existence of a feedback loop on older and more intensively browsed saplings. As such, our study provides empirical evidence that morphological and physiological trait responses to browsing influence oak sapling attractiveness, but that the direction and magnitude of this effect depend on the ontogenic stage of the sapling and on the number of browsing events.

Les instituts de recherche en productions animales des pays du Sud disposent parfois de laboratoires d'analyse. Cependant ces laboratoires rencontrent souvent des difficultés de fonctionnement soit techniques (défaut d'approvisionnement en eau ou électricité) soit humaines (difficultés à avoir et/ou conserver des agents formés). De plus, les centres de recherche disposent parfois de capacités d'investissement en équipements scientifiques assez bonnes (projets, coopération, dons) mais ne disposent pas des ressources financières pour les maintenir et les faire fonctionner correctement. La production de données de référence fiables est donc généralement très difficile et aléatoire. Dans ce contexte où il est également de plus en plus difficile de faire voyager des échantillons pour des raisons sanitaires ou réglementaires, l'utilisation de la SPIR est une solution efficace pour permettre la production de données expérimentales à grande échelle. L'UMR Selmet travaille à la mise en place d'un réseau SPIR en Afrique et Océan Indien. Cette stratégie vise à appuyer nos partenaires d'une part à s'équiper en SPIR pour leur permettre d'acquérir une capacité de caractérisation de leurs ressources alimentaires et d'autre part à les accompagner dans le développement de cette technique. Pour l'UMR Selmet l'accompagnement des partenaires passe par la formation et par le développement et le déploiement d'outil d'aide à la prédiction (plateforme de prédiction en ligne " NIRSPred "). Il est cependant essentiel d'associer les partenaires à la production de données de référence et d'éviter de les rendre totalement dépendants de bases centralisées. L'aide au suivi de la qualité des spectromètres (création automatisée de carte de contrôle " ASDMonitor ") est également un élément important de l'appui au développement du réseau.

Certains échantillons de végétaux conservés dans des collections (échantillothèques, herbiers, carpothèques, …) ont une valeur scientifique ou patrimoniale importante, et la mesure de leurs caractéristiques biochimiques par SPIR serait intéressante. Une limite à cette utilisation peut être l'état de conservation des échantillons et ses conséquences sur leur composition chimique. Dans le cadre de la valorisation d'importantes collections d'aliments pour animaux (plus de 60 000 échantillons stockés depuis les années 1960), nous avons étudié l'évolution des spectres et des prédictions de composition chimique avec la durée de stockage d'échantillons de fourrages. 120 échantillons appartenant à 4 catégories de végétaux ont été sélectionnés. Les spectres des échantillons présentés en poudre ont été collectés sur un spectromètre FOSS (NIRSYSTEM 5000 et 6500, 1100-2500nm) en 2002 puis à nouveau en 2017. Deux types de comparaisons ont été réalisées, l'étude de l'évolution du spectre et l'étude de l'évolution des prédictions de trois paramètres clé : protéines (MAT), fibres totales (NDF) et digestibilité in vitro (DMO). La distance entre les spectres initiaux et les spectres obtenus après 15 ans est supérieure à celle observée entre deux répétitions réalisées à la même date. Une partie des différences est logiquement située dans les bandes de l'eau mais certaines se situent dans d'autres régions spectrales. Les valeurs de prédictions montrent (i) que les résultats sont comparables pour les paramètres MAT et DMO, (ii) qu'il y a une diminution de la teneur en NDF pour toutes les catégories d'échantillons, (iii) que les écarts-types sont identiques pour un même paramètre. Les régressions linéaires entre les prédictions basées sur les anciens et les nouveaux spectres donnent des R² autour de 0,96. Malgré le biais qu'il peut y avoir, les valeurs restent fortement corrélées. Il est donc nécessaire de prendre des précautions dans l'interprétation des données de prédictions sur des échantillons anciens. D'une part, celles-ci devraient être réalisées à partir d'équations n'intégrant pas les bandes de l'eau. D'autre part, l'existence d'un biais systématique sur certains paramètres doit être prise en compte, en effectuant des comparaisons sur des valeurs relatives plutôt qu'absolues. Une étude sur la dynamique des changements observés au cours du temps pourrait montrer si l'évolution concerne essentiellement les premiers temps de stockage ou si elle se poursuit au cours du temps.

Dans le cadre du projet Biomass For the Futur (BFF), des échanges inter-laboratoires d'échantillons de miscanthus, sorgho et maïs sont effectués afin de mesurer et de prédire des paramètres biochimiques. Chaque laboratoire possède ses propres méthodes de mesures expérimentales et ses modèles de calibration proche infrarouge. A ce jour, les prédictions issues des modèles de calibration nécessitent l'acquisition de spectres au laboratoire. L'objectif du travail mené ici est de pouvoir s'affranchir de cette étape d'acquisition en créant des modèles de transfert entre deux spectromètres. En effet, les appareils des laboratoires partenaires sont de marques différentes, et n'ont pas les mêmes modalités d'acquisition (unités, résolution…). Il est donc nécessaire de créer des modèles permettant de transférer un spectre d'un appareil vers un autre afin de l'utiliser pour la prédiction de paramètres biochimiques. La présentation repose ici sur les modèles de transfert entre l'UMR SELMET pour leur spectromètre FOSS NIRSystem5000, et le LBE pour le spectromètre BUCHI N-500. Les modèles de transfert sont réalisés sur ChemFlow, logiciel de chimiométrie gratuit en ligne, permettant le stockage et le partage de données entre utilisateurs. Deux types d'échantillons ont été échangés entre ces deux laboratoires pour la création des modèles : 40 échantillons de référence, représentatifs des activités de chaque laboratoire, ainsi que 31 échantillons spécifiques du projet BFF (maïs, miscanthus et sorgho). Ces deux jeux de données ont dans un premier temps été pris séparément pour créer deux modèles : le modèle labo40 (global) et le modèle BFF31 (local). Puis dans un second temps, les 71 échantillons sont rassemblés pour créer le modèle globalBFF71. Ces trois modèles sont construits avec l'outil de transfert PDS (Piecewise Direct Standardization) et diffèrent seulement par leur jeu de construction. Enfin, un modèle témoin est testé, le modèle 0, créé sans outil de transfert, simplement avec des fonctions permettant de changer les modalités du spectre (unité, absorbance ou réflectance, lissage et interpolation de spectres). Le but est de sélectionner le modèle qui donnera les meilleurs spectres transférés mais également de comparer les modèles globaux et locaux. Deux jeux de validation sont utilisés pour la comparaison de ces quatre modèles : 11 échantillons de sorgho et 24 de miscanthus. Les valeurs biologiques des paramètres biochimiques étudiés sont connues, les spectres proche infrarouge ont été acquis sur le BUCHI ainsi que sur le FOSS, les prédictions laboratoires sont donc également connues (matière minérale totale, fibres, cellulose, digestibilité, potentiel méthane…). Les spectres des deux jeux de validations ont été transférés du BUCHI vers le FOSS et inversement, suivant les quatre modèles de transfert et les prédictions des paramètres biochimiques ont été réalisées sur les quatre nouveaux spectres transférés. Les tracés des spectres issus des différents modèles montrent des déformations ainsi que des décalages d'absorbance ou de réflectance comparables pour chaque modèle. Grace aux tracés du spectre cible en fonction du spectre transféré, il est possible d'identifier des déformations plus importantes pour le modèle local BFF31. La comparaison entre les valeurs biologiques et les prédictions sur spectres transférés pour le potentiel méthane, permet difficilement de sélectionner le meilleur modèle (erreurs de prédiction comprises entre 15 et 20 mLCH4/gMV). Cependant, avec d'autres paramètres comme la digestibilité, des erreurs de 5,8% et 5,3% pour les modèles labo40 et globalBFF71 sont observées, contre 14,3% pour le modèle BFF31. En revanche, ce dernier montre des résultats plus intéressants suite à la comparaison des coefficients de Kendall (coefficient de corrélation de rang) pour plusieurs paramètres biochimiques. Suite à l'étude de l'ensemble des critères de comparaison, la sélection du modèle final sera en faveur d'un modèle global.

The objective of this study was to contribute to the characterization of nutritional potentials, with special attention to the total phenol and condensed tannins content and the effects on in vitro digestibility of some browsing shrub legumes traditionally used for ruminant feeding. The varieties selected were Bituminaria bituminosa var. bituminosa (BBB), Bituminaria bituminosa var. albormaginata (BBA), Chamaecytisus proliferus var. palmensis (CPP), Chamaecytisus proliferus var. canariae (CPC), and Adenocarpus foliosus (AF). Chemical composition, in vitro digestibility, and net energy for lactation (NE) were analyzed and compared among varieties; the effects of total phenol (TP) and condensed tannins (CT) compounds on digestibility were estimated. Condensed tannins ranged from 1 to 5 g/kg DM of tannins, while total phenols ranged from 9 to 32 g/kg DM of tannins. In vitro organic matter digestibility (OMD) ranged from 0.52 to 0.71, and estimated net energy for lactation (NE) ranged from 4.2 to 5.8 MJ/kg DM, with significant differences among all the varieties. This Chamaecytisus varieties (CPC, CPP) have higher feeding values, following CPC > CPP > AF > BBB > BBA in order. Although there were condensed tannins and total phenols in all the shrubs analyzed, total phenol contents differed significantly between the shrubs. The effect of the content of the total phenols and of the tannins condensed in the OMD of the varieties of shrubs analyzed, shows that the higher amounts of total phenols in some of the varieties of shrubs analyzed, increased the in vitro digestibility (OMD) of the shrubs but high amounts of CT decreased OMD.

With its high biomass yield potential and its adaptability to a large spectrum of crop management schemes (dedicated, double cropping), sorghum is a relevant candidate crop for anaerobic digestion. Moreover, the large genotypic variability of its biochemical composition offers opportunities to cultivate specific varieties that fit the expectations of different end-users. Within this context, the need to evaluate the variability of biomethane potential (BMP) among different genotypes cultivated at various geographical sites has become crucial. In this study, four sorghum genotypes were grown at three different sites and harvested at the same maturity stage (dough grain stage). Consistent BMP obtained from different assays enabled genotype comparisons. The methane potentials observed between genotypes and production sites ranged between 200 ± 5 NmLCH4/gTS and 259 ± 12 NmLCH4/gTS. Evaluation of the genotypic and cultivation site effects produced highly significant results, thus accounting for 36 and 34%, respectively, of the phenotypic variability.

International audience; The thickness of grain pericarp, the outer layer of the kernel, is an important breeding criterion for sorghum. This cereal is mainly used through traditional processing in family-based food systems in many regions of the world. We investigated in this study how pericarp thickness could be predicted by Near Infrared Reflectance Spectroscopy (NIRS), a fast and non-destructive measurement method that is commonly used to measure physico-chemical parameters of sorghum grains, and how this trait also influences the prediction of those parameters. We showed that, using a classification approach, it was possible to discriminate thick from thin pericarp whole grain samples with a good accuracy and that the proportion of thin and thick grains in mixed samples could also be predicted. In addition, pericarp thickness had a significant effect on the calibration performance for other grain parameters indicating that the pericarp can distort spectral information of whole grain samples. As a practical consequence, we suggest to develop separate whole grain calibration models for thin and thick pericarp samples, combined with a two-steps prediction approach to improve the accuracy of whole grain NIRS calibrations for grain quality parameters in sorghum.

Two experiments were conducted to investigate the use of sorghum, cottonseed meal and millet in broiler diets and their interaction when they are used simultaneously. In Experiment 1, a corn-soybean meal control diet was compared with eight experimental treatments based on low tannin sorghum (S30, S45 and S60), cottonseed meal (CM15, CM40) or both ingredients included in the same diet (S30/CM40, S45/CM25 and S60CM15). Results showed that BW gain was not affected by the inclusion of sorghum or cottonseed meal. However, feed intake tended to be affected by the cereal type with the highest values with sorghum-based diets. Feed conversion ratio increased (P

International audience; In the dataset presented in this article, sixty sugarcane samples were analyzed by eight visible / near infrared spectrometers including seven micro-spectrometers. There is one file per spectrometer with sample name, wavelength, absorbance data [calculated as log10 (1/Reflectance)], and another file for reference data, in order to assess the potential of the micro-spectrometers to predict chemical properties of sugarcane samples and to compare their performance with a LabSpec spectrometer. The Partial Least Square Regression (PLS-R) algorithm was used to build calibration models. This open access dataset could also be used to test new chemometric methods, for training, etc.

International audience; Sorghum is expected to contribute significantly to the growing needs of ligno cellulosic biomass that will support the productions of renewable energy, biomaterials and innovative biorefinery approaches. The agronomic and genetic assets of sorghum will facilitate these contributions. Nevertheless, in order to fine tune the varieties to the expectations of the growers (agronomic behavior) and of the different value chains (quality parameters) there is a crucial need to i) optimize the production process of sorghum based derived products and ii) to accurately define the target ideotypes to consider in breeding programs depending on the end-products and contexts considered. As a first step, we considered three end products: methane, biocomposite and feed. For the first two targets, we optimized the process of production by adjusting the pre-treatments and fine tuning-the different steps of the processes. As a second step we aimed at identifying the sorghum traits that contributed to the final properties of the end products. To reach this objective, we characterized at the biochemical, histological and physical levels a panel of diversity that encompassed most of the chemical variability of sorghum biomass. This panel was also characterized for its feed and biocomposite properties and for its biomethane production potential. This allowed the identification of the sets of biomass properties to target for the different end-products. As a last step, specifically for the energy targets (methane and second generation ethanol), we performed a spatially based multicriteria analysis at the regional level (anchoring the analysis on the French Midi Pyrenées region) to assess the relevance of different types of crop management and end product value chains in accordance with the local constraints (i.e. water availability, technical context). These three steps provided us with a decision tool to orientate breeding efforts depending on the targeted end-product, the environmental and technical contexts.

The management of livestock systems for technical, economic and environmental optimization requires an increasingly accurate formulation of rations and therefore a detailed knowledge on the feeds consumed by animals. Near-infrared spectrometry (NIRS), which has been used increasingly since the 1960s, is an analytical technique that allows rapid characterization of feeds or forage samples. The first applications developed were on the chemical composition of the feeds, but it is also possible to develop calibrations for the estimation of the nutritional value and the feed intake. Beyond these direct measurements on the feed, NIRS can also be applied to faeces to characterize the feeding of animals on rangelands. Joint consideration of feed and feces spectra can give a picture of how animals actually use feeds. Other possible uses of NIRS such as traceability or feed classification and botanical recognition of plants in grasslands are also described. The current technical developments, and in particular the miniaturization of spectrometers, make it possible to bring the instruments on the field to produce information as close as possible to its use. Other spectroscopic techniques that are alternative or complementary to NIRS such as mid-infrared spectroscopy, Raman spectroscopy or hyperspectral imaging will allow other measurement conditions and other applications., Le pilotage des systèmes d’élevage en vue d’une optimisation technique, économique et environnementale passe par une formulation des rations de plus en plus précise et nécessite donc une connaissance fine des aliments consommés par les animaux. La spectrométrie dans le proche infrarouge (SPIR), utilisée de façon croissante depuis les années 60, est une technique analytique permettant de caractériser rapidement des échantillons d’aliments ou de fourrages. Les premières applications concernaient la composition chimique des fourrages, mais il est également possible de développer des étalonnages pour une estimation de la valeur nutritive et de l’ingestion. Au-delà de ces mesures directes sur l’aliment, la SPIR peut être appliquée sur les fèces afin de caractériser l’alimentation d’animaux sur parcours. Le traitement conjoint des spectres des aliments et des fèces peut donner une vision de l’utilisation réellement faite des aliments par les animaux. D’autres utilisations possibles de la SPIR comme la traçabilité ou la classification des aliments ainsi que la reconnaissance botanique des végétaux dans les prairies sont aussi décrites. Les développements techniques actuels, et notamment la miniaturisation des spectromètres, permettent d’amener les instruments sur le terrain pour produire l’information au plus près de son utilisation. D’autres techniques spectroscopiques alternatives ou complémentaires à la SPIR comme la spectroscopie dans le moyen infrarouge, la spectroscopie Raman ou l’imagerie hyperspectrale permettront d’autres conditions de mesures et d’autres applications.

International audience; Composites prepared with whole sorghum stem fragments reinforcing a polyethylene matrix were studied using ten different sorghum genotypes. Using a robust processing protocol, it is shown that for a given sorghum genotype, the composition of the stem fragments varies depending on the size of the sieved fragments but with the genotype effect being larger than the sieving effect. There is a variation of mechanical properties between the genotypes (from 0.6 to 1 GPa for modulus, from 7.2 to 11.5 MPa for tensile strength and from 4.4 to 6.2 kJ/m2 for impact strength). The genotypes giving the best tensile mechanical properties are the ones which have the highest viscosity, which show during blending the largest energy dissipation and which have the less decrease of size after processing. There is a weak correlation between tensile mechanical properties and resistance to impact suggesting that it is not the same tissues or physical properties which contribute to these two tests.

Le régime alimentaire des animaux d'élevage qui se nourrissent dans les parcours méditerranéens de garrigue peut comprendre plus de 50 aliments (" plante prise ", PxP) par jour. Sa composition change en fonction des jours et des saisons. Ainsi, une évaluation classique de la valeur nutritive de l'alimentation avec un échantillonnage des fourrages disponibles suivi d'une analyse chimique serait trop difficile, et la grande masse de résultats produit ne serait pas exploitable de façon opérationnelle. Nous explorons une méthode alternative pour caractériser la diversité des aliments disponibles en regroupant les échantillons en classes nutritives fonctionnelles par une classification basée sur les spectres. La zone étudiée était une garrigue méditerranéenne (Corconne, Gard), pâturée par des ovins. En se basant sur le comportement alimentaire des moutons, des prélèvements de PxP ont été effectués sur 3 saisons (Mai 2015, Juin et Octobre 2016). Un total de 358 échantillons a été collecté, appartenant à 66 espèces végétales. Les échantillons ont été séchés à l'étuve (55°C) et broyés (1mm) avant la collecte des spectres proche infrarouge (NIR, 1100-2500 nm). Les spectres ont été prétraités (dérivée d'ordre 2 ; SNV et detrend) et les bandes correspondant à l'absorption de l'eau ont été éliminées pour éviter que le classement ne se fasse sur la base de l'humidité résiduelle des échantillons. Une classification hiérarchique des spectres NIRS a été effectuée, conduisant à la définition d'un nombre limité de classes. Certaines classes étaient relativement homogènes au plan botanique (par exemple essentiellement des espèces de graminées) alors que d'autres rassemblaient des plantes très diverses au plan botanique, mais ayant une valeur nutritionnelle et / ou des caractéristiques similaires, telles que la nature des organes (jeunes feuilles tendres, tiges lignifiées etc.) ou la présence de composés secondaires comme des huiles essentielles. Cette méthode pourrait permettre une meilleure caractérisation de la valeur des parcours pour une exploitation par les animaux. L'enrichissement des bases de données par des échantillons collectés dans des milieux divers permettra une plus grande universalité des classes constituées par cette méthode.

In aquaculture, it is extremely important to determine the composition of fish farm waste to evaluate its potential impacts and to improve its reuse. Near-infra red spectroscopy (NIRS), an alternative to standard chemical analytical techniques, is a quick non-invasive method to assess physical and chemical composition, reducing the cost of routine analysis. We developed NIRS calibration models for organic matter (OM), total organic carbon (TOC), total organic nitrogen (TON), the carbon/nitrogen ratio (C/N), total phosphorus (TP) and the lipid content of marine fish particulate waste. To obtain a wide range of compositions of fish waste, decomposition time, feed loss, and inter-specific variations were taken into account. The NIRS calibration models were built using three sub-datasets: in Scenario 1) the calibration was species-specific, including only seabass waste (SeabassWaste), in Scenario 2), the calibration included data from two other species (MultiSpeciesWaste) and in Scenario 3), the general calibration included all data as well as simulation of extreme feed loss (up to 50%) (Faeces & Feed). All calibrations performed using either dried or wet samples gave equations with high coefficients of determination (R-2) and reasonably low standard error of cross validation (SECV) values for all parameters tested, except for TP due the high proportion of mineral P.

Following the tribal allocation of land in the 1920s and the development of agriculture in the wadi area, the last six decades have seen the settlement of the majority of Bedouin tribes in Egypt. In the two last decades, the Bedouin in the Coastal Zone of the Western Desert had to cope with a severe 15-year drought combined with major changes in link with tourism, urbanization, and agricultural development. Using data collected in surveys and interviews, we show that the adaptive processes of the Bedouin are embedded in their social organization and in their ability to adopt new activities.

Improving feed efficiency remains crucial for poultry production. Birds have previously been selected on their ability to digest their diet, as assessed by AMEn (Apparent ME corrected for 0 nitrogen). Such selection, for either a high (D+) or a low AMEn (D-), affects energy, nitrogen, lipid, and starch digestibility. The aim of this study was to establish whether selection on the digestive ability of birds modified metabolic traits. A total of 630 broiler chickens of the eighth generation of a divergent selection experiment on AMEn were used for this purpose. A balance trial was performed to determine energy, nitrogen, and phosphorus retention. Growth performance was recorded and body protein and lipid deposition assessed by breast and abdominal fat yields. Tibia development and mineralization were also studied and heat production was indirectly assessed through the measurement of body temperature during fasting and feeding. Phenotypic correlations estimated within line showed that an increased efficiency was associated to fatter birds and more solid bones in D- but not in D+ line, whereas increased consumption was associated with more solid bones in D+ but not in D- line. The heritability estimates for metabolic traits were relatively high, except for temperature traits (from 0.08 to 0.12), ranging from 0.28 to 0.56 for body composition, and from 0.38 to 0.77 for bone characteristics. Breast meat yield did not differ between the 2 lines whereas a slight increase in abdominal fat yield was observed in the high-digestion line (D+). The relative dry tibia weights and ash weights were greater in D+ birds (+6.56 and +8.06%, respectively) but the lengths and the diameters of the tibia were lower (-7.89 and -3.77%, respectively). Finally, AMEn was poorly correlated with almost all metabolic traits (ranging from -0.10 to 0.20), indicating that the ability of the animal to digest its diet is genetically independent of post-digestion metabolic traits.

The mule duck, an interspecific hybrid obtained by crossing common duck (Anas platyrhynchos) females with Muscovy (Cairina moschata) drakes, is widely used for fatty liver production. The purpose of the present study was to detect and map single and pleiotropic QTL that segregate in the common duck species, and influence the expression of traits in their overfed mule duck offspring. To this end, we generated a common duck backcross (BC) population by crossing Kaiya and heavy Pekin experimental lines, which differ notably in regard to the BW and overfeeding ability of their mule progeny. The BC females were mated to Muscovy drakes and, on average, 4 male mule ducks hatched per BC female (1600 in total) and were measured for growth, metabolism during growth and the overfeeding period, overfeeding ability, and the quality of their breast meat and fatty liver. The phenotypic value of BC females was estimated for each trait by assigning to each female the mean value of the phenotypes of her offspring. Estimations allowed for variance, which depended on the number of male offspring per BC and the heritability of the trait considered. The genetic map used for QTL detection consisted of 91 microsatellite markers aggregated into 16 linkage groups (LG) covering a total of 778 cM. Twenty-two QTL were found to be significant at the 1% chromosome-wide threshold level using the single-trait detection option of the QTLMap software. Most of the QTL detected were related to the quality of breast meat and fatty liver: QTL for meat pH 20 min post mortem were mapped to LG4 (at the 1% genome-wide significance level), and QTL for meat lipid content and cooking losses were mapped to LG2a. The QTL related to fatty liver weight and liver protein and lipid content were for the most part detected on LG2c and LG9. Multitrait analysis highlighted the pleiotropic effects of QTL in these chromosome regions. Apart from the strong QTL for plasma triglyceride content at the end of the overfeeding period mapped to chromosome Z using single-trait analysis, all metabolic trait QTL were detected with the multitrait approach: the QTL mapped to LG14 and LG21 affected the plasma cholesterol and triglyceride contents, whereas the QTL mapped to LG2a seemed to impact glycemia and the basal plasma corticosterone content. A greater density genetic map will be needed to further fine map the QTL.

Improving the sustainability of poultry production involves limiting its environmental impact and maintaining effectiveness. It has recently been shown that genetic selection on the ability of chickens to digest wheat at 23 d of age can decrease chicken excretion without decreasing BW at this age. The aim of this study was to check whether selection on digestibility modifi ed excretion and growth performance over the whole production cycle. The 2 divergent lines selected for high (D+) and low (D-) apparent metabolizable energy corrected for 0 N balance (AMEn) values were compared with a reference line used at the beginning of the selection experiment (RL) to evaluate the potential excretion improvement that could be expected with such selection. These 3 lines were therefore compared for growth and excretion (raw and relative to feed intake, fresh and dry excreta weights, and moisture content of excreta) from 4 to 53 d. Between 4 and 7 d, 17 and 21 d, and 49 and 53 d, AMEn and N and P excretion rates were also compared between the 3 lines. Furthermore, body composition (breast meat and abdominal fat yields), bone breaking strength, and meat quality traits (lightness, redness, yellowness, and ultimate pH) were compared between lines at 53 d. Over the whole rearing period, D+ birds excreted signifi cantly less fresh and dry excreta (?56 and ?61%) than D- and RL birds (?6 and ?26%). Similarly, N and P excretion rates of D+ birds were 13% to 30% less than those of D- birds and 12% to 19% less than RL birds, depending on age. These excretion differences may be related to the differential development of the gastrointestinal tract. Differences between lines were already present at 7 d for relative gizzard weight and the weight of the upper to the lower part of the gastrointestinal tract ratio. Anatomic differences were maximum at 23 d for all traits except for relative weight of the duodenum. At slaughter age, BW, breast and fat yields, and meat color did not differ between D+ and RL birds, but D- birds were fatter than D+ and RL birds. Finally, ultimate meat pH was 1% to 2% greater in RL birds than in the D+ and D- lines. In conclusion, this study showed that selection of chickens for AMEn is a possible way to reduce the environmental impact of production over the whole rearing period without a negative impact on growth, body composition, or meat quality. (Resume d'auteur)

National audience

In the framework of studies on the nutritional value of rangeland plants, it can sometimes be useful to have an indication of the lipid content of samples, although it is not a major component of plant vegetative parts. Heterogeneous databases gathering very diverse plants or plant parts require a very large number (several hundreds) of chemical analyses for calibration of chemical composition, so that lipids are generally not considered in such databases. The present study intends to seek for a proxy of lipid content as a single wavelength in the NIR spectrum. The objective is not to predict lipid content, but to be able to rank the plants according to their lipid content. The study is based on samples from a study on Mediterranean shrubby rangelands (“garrigue”) with mixed vegetation: grasses, shrubs, trees (Silué et al., 2016). About 250 samples from 60 species were collected in Corconne (southern France). Samples were dried mildly (55°C) and ground (1mm sieve). Spectra were collected on a FOSS NIRSYSTEM 5000 spectrometer with a wavelength range 1100-2500nm (2mm step). Then 30 samples were selected to represent the botanical diversity and the expected range of lipids. Lipid content was assessed by crude fat analysis by extraction with petroleum ether on Soxhlet. The approach was to correlate lipid content with absorption at individual wavelength, in order to identify wavelengths better representing lipids. This analysis was performed on raw spectra as well as on spectra pretreated with different derivation orders and smoothing options. The correlogram for 2nd derivative is shown as an illustration on Figure 1. The highest correlations obtained with the different pretreatements were R²=0.04 (at 1402nm) with raw spectra, 0.29 (at 1760nm) with 1st derivative, 0.63 (at 1772nm) with 2nd derivative, 0.64 (at 1782nm) with 3rd derivative. The correlation with wavelengths in the 1760-1780nm is high enough to provide a useful information on lipid content. When applied to the whole database, the lipid ranking identified the plants high in lipids (genera: Juniperus, Erica, Pinus, Rosmarinus, Asparagus, Dorycnium…) or low in lipids (Arbutus, Cistus, Asphodelus, Rubia, Hedera, Rhamnus …). However a proper validation with additional reference analyses has to be done. The high correlations with individual wavelengths suggest that a calibration of lipid content in such a database would be possible. However it would require many analyses, which is not relevant on the short term because accurate prediction of lipid content is not required. The proxy can help identifying the low / intermediate / high lipid plant parts, and can contribute to explain the feeding behavior of animals. It can also help for the selection of samples to be analyzed in the laboratory. A similar approach will be tested on fresh samples, since all samples were also scanned before drying: at this stage the volatile essential oils are still present in the samples and will provide more accurate information on secondary compounds present in the fresh plants.

Polyethylene glycol (PEG) measured with NIRS is known to be a valuable faecal marker when used in indoor experiments. In order to verify whether it can be used at pasture, an experiment was conducted with two trials. In trial 1, six Romane breed adult dry ewes placed in metabolism cages were fed daily with natural, freshly cut rangeland from a fertilised or unfertilised paddock for 6 weeks. Three ewes did not receive PEG and the three others were dosed with 10 g of PEG in solution form once daily until the end of the experiment to measure in vivo dry matter digestibility and PEG recovery rate for each forage quality. At the same time (trial 2), 15 ewe lambs and 14 lactating adult ewes suckling one or two lambs were allowed to graze together on the same herbage as that cut for indoor ewes. All animals were initially equipped with faecal bags emptied twice daily for collecting total faeces, and eight ewe lambs and seven adults were dosed once daily with 10 g of PEG. Faecal grab samples were collected for 4 to 5 days for each forage quality grazed. Indoor trial 1 showed that PEG had no effect on dry matter intake (DMI) or on digestibility. PEG recovery rates measured on fertilised (77.7%) and unfertilised (82.1%) forage were not different ( P>0.05). PEG recovery rates measured at pasture did not differ( P>0.05) between pasture quality and animal type with an average value of 68.9%. Faecal output measured with bags or estimated with PEG and calculated DMI were not different ( P>0.05) when PEG recovery rate measured at pasture was used. Conversely, using indoor PEG recovery values, significantly ( P