CONTRIBUTIONS DES PARTENARIATS POUR CONCEVOIR DES CONNAISSANCES AGRONOMIQUES SUR LA GESTION DE L'HERBE ET DEVELOPPER DES OUTILS ACTIONNABLES PAR DES CONSEILLERS FOURRAGERS

N° ISBN - 978-2-7380-1284-5International audienceCo-design of artifacts usable by extension services can be a long-lasting task. It partly depends on the developments of scientific knowledge. In addition, as we will show in this testimony, training and partnership with practitioners play a key role in the design of an artifact, here a tool to diagnose the opportunity of grassland management practices in a farm. Discussions between researchers and practitioners during training sessions led to the design of prototypes of articfact. Partnership between researchers and practitioners on the long term contributed to adjust the artifact, to simplify its procedure, and overall to improve its diagnosis capacity by capitalizing on researchers' and practitioners' knowledge. This experience has required adaptive capacity of researchers, leading them to adopt different research postures according to the stages in the interactions with practitioners. Researchers considered practitioners as knowledge providers by associating them to articfact co-design, or as experts to be equipped by involving them in participatory research projects

The [FeFe] hydrogenase of Nyctotherus ovalis has a chimeric origin

BACKGROUND: The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I. RESULTS: The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome. CONCLUSION: The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering

Etude des mécanismes chimiques impliqués dans la complexation des mycotoxines par les composants de la paroi cellulaire de la levure Saccharomyces cerevisiae

CLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

La biomasse pariétale des fourrages et sa valorisation par les herbivores

National audienceCell-wall carbohydrates arising from photosynthesis produce large amounts of biomass. Some of this lignocellulose can only be effectively used by herbivores thank to the microorganisms living in the digestive tracts. The ruminant is the most studied herbivore. It was used in the studies as a model for the process of anaerobic degradation of lignocellulosic compounds and to study the specific role of the different micro-organisms in the rumen (bacteria, protozoa, fungi). The products of the microbial metabolism (volatile fatty acids - vitamins) are used by the host animal. Furthermore, the microbial biomass constitues the main supply of animo-acids to the ruminant. Some very lignified forages are not easy hydrolysed by the microorganisms. The main difficulty is the large amount of lignin they contain. It is possible to improve their degradation by three methods. 1°) Using of appropiate technology. Alkali treatments are economic and, especially ammonia, increasingly used, whereas grinding and steam treatment are only attractive in certain situations. Sometimes, white fungi treatments have produced interesting results but are still at laboratory and pilot stage and need further improvements. Other chemical (oxidants, SO2), physical (irradiation) and biological (enzymes, bacterial protein enrichment) treatments are presently uneconomic and only partially tested on animals, but they have provided interesting information on the relationship between cellwall structure and degradability. In any event, upgrading of crop residues by best treatments presently available only increases digestibility to 0.5 - 0.6. 2°) Optimization of the bacterial activity in the rumen can be achieved by providing the organisms optimum quantities of the nutrients they need. In addition, genetical engineering opens up prospects for the improvement of bacterial muralytic enzymes activity, especially in unfavourable media (cellulolysis in low pH media). 3°) Optimization of morphologic and physiologic characteristics of the digestive tract can be attained examining the possibilities offered by different animals according to the position of the fermentation chamber (herbivores with fermentor at the beginning or at the end of the digestive tract) and by the characteristics of the fermentor (capacity, retention time of solid particles, turn over rate of liquid, distribution of liquid and solid phases...). This approach is particulary interesting for countries oriented towards the utilization of low quality crop residuesAu sein de la biomasse végétale, les composés à teneur élevée en parois constituent une source d’aliments que seuls les herbivores peuvent utiliser. Parmi les herbivores, le Ruminant a été de loin le plus étudié. Les processus de dégradation anaérobie des composés lignocellulosiques dans le rumen mettent en jeu le rôle spécifique des micro-organismes (bactéries, protozoaires, champignons). Les produits du métabolisme microbien sont directement utilisés par l’animal hôte comme source d’énergie (acides gras volatils) ou comme principal fournisseur d’acides aminés (protéines microbiennes synthétisées dans le rumen) ou de vitamines (vitamines B). La teneur en lignine élevée de certains fourrages est cause d’une médiocre dégradation par les micro-organismes du tube digestif. Il est possible d’améliorer leur utilisation par trois moyens. Les traitements technologiques sont très nombreux mais seuls ceux aux alcalis, surtout à l’ammoniac, et, dans certains cas le broyage et les traitements hydrothermiques sont économiquement rentables et se développent dans la pratique. Les procédés aux moisissures blanches doivent encore être développés. Les autres traitements chimiques (oxydants, SO2) physiques (irradiation) et biologiques (enzymes, bactéries apportant des nutriments), ne sont pas suffisamment rentables. Les améliorations apportées par les meilleurs traitements ne permettent pas cependant de dépasser une digestibilité de 0,5 - 0,6 pour les résidus très lignifiés. Les recherches futures doivent développer d’autres voies tout en perfectionnant (efficacité, économie) les procédés actuels. L’optimisation de l’activité microbienne dans le rumen peut être atteinte en fournissant aux microbes les nutriments dont ils ont besoin. En outre, l’emploi du génie génétique ouvre des perspectives dans l’amélioration de la production d’enzymes microbiennes particulièrement efficaces à l’égard des parois ou en permettant le développement de certaines activités microbiennes dans des conditions de milieu peu favorables (cellulolyse en milieu de pH faible). L’optimisation des fermentations peut être atteinte en choisissant le type d’herbivore dont les caractéristiques morphologiques et physiologiques des réservoirs de fermentation sont optimisées, en premier lieu par leur position (rumen ou gros intestin) puis en sélectionnant divers critères (capacité, temps de séjour des aliments, répartition des phases liquides et solides, ...). Cette approche est d’un intérêt considérable pour les pays qui s’orientent vers un système d’utilisation des résidus très lignifiés de l’agriculture

Intake and digestibility of different forages in Hamas compared to sheep

International audienc

Rumen protozoa and methanogenesis: not a simple cause–effect relationship

10 páginas, 4 tablas, 1 figura.Understanding the interactions between hydrogen producers and consumers in the rumen ecosystem is important for ruminant production and methane mitigation. The present study explored the relationships between rumen protozoa, methanogens and fermentation characteristics. A total of six donor sheep harbouring (F, faunated) or not (D, defaunated) protozoa in their rumens (D animals were kept without protozoa for a period of a few months (D2) or for more than 2 years (Dþ)) were used in in vitro and in vivo experiments. In vitro the absence of protozoa decreased NH3 and butyrate production and had no effect on methane. In contrast, the liquid-associated bacterial and methanogens fraction of Dþ inocula produced more methane than D2 and F inoculum (P,0·05). In vivo fermentation parameters of donor animals showed the same trend on NH3 and butyrate and showed that Dþ animals were high methane emitters, while D2 were the lowest (235 %). The concentration of dissolved dihydrogen measured after feeding followed the opposite trend. Methane emissions did not correlate with the relative abundance of methanogens in the rumen measured by quantitative PCR, but there was a trend for higher methanogens concentration in the solid-associated population of Dþ animals compared with D2 animals. In contrast, PCR-denaturing gradient gel electrophoresis profiles of methanogens’ methyl coenzyme-M reductase A gene showed a clear clustering in liquid-associated fractions for all three groups of donors but fewer differences in solid-associated fractions. These results show that the absence of protozoa may affect differently the methanogen community and methane emissions in wethers.The present study was supported by the French National Institute of Agricultural Research (INRA). D. P. M. and M. J. R. conceived and designed the study and carried out the primary data analysis and experimental work. D. P. M. wrote the manuscript. C. M. and J.-P. J. contributed to the statistical analysis and discussion of the results. All authors revised the manuscript. There are no conflicts of interestPeer reviewe

Methane production by ruminants: its contribution to global warming

The aim of this paper is to review the role of methane in the global warming scenario and to examine the contribution to atmospheric methane made by enteric fermentation, mainly by ruminants. Agricultural emissions of methane in the EU-15 have recently been estimated at 10.2 million tonnes per year and represent the greatest source. Of these, approximately two-thirds come from enteric fermentation and one-third from livestock manure. Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation and this paper considers in detail the reasons for, and the consequences of, the fact that the molar percentage of the different volatile fatty acids produced during fermentation influences the production of methane in the rumen. Acetate and butyrate promote methane production while propionate formation can be considered as a competitive pathway for hydrogen use in the rumen. The many alternative approaches to reducing methane are considered, both in terms of reduction per animal and reduction per unit of animal product. It was concluded that the most promising areas for future research for reducing methanogenesis are the development of new products/delivery systems for anti-methanogenic compounds or alternative electron acceptors in the rumen and reduction in protozoal numbers in the rumen. It is also stressed that the reason ruminants are so important to mankind is that much of the world's biomass is rich in fibre. They can convert this into high quality protein sources (i.e. meat and milk) for human consumption and this will need to be balanced against the concomitant production of methane.Production de méthane par les ruminants : sa contribution au réchauffement de la planète. Cet article examine le rôle du méthane dans le processus de réchauffement de la planète et évalue la contribution au méthane atmosphérique des gaz d'origine digestive issus principalement des ruminants. Les émissions annuelles de méthane d'origine agricole dans l'Europe des quinze ont été estimées récemment à 10,2 millions de tonnes et représentent la principale source des entrées atmosphériques de méthane. Parmi celles-ci, approximativement les deux tiers proviennent des fermentations entériques et un tiers des lisiers. Le méthane ruminal représente environ 90 % de l'ensemble des fermentations digestives. Le présent article analyse en détail l'impact des orientations fermentaires sur la production de méthane dans le rumen. L'acétate et le butyrate favorisent la production de méthane tandis que la formation de propionate constitue une voie alternative d'utilisation de l'hydrogène dans le rumen. Les différentes possibilités offertes actuellement pour diminuer les émissions de méthane sont analysées, à la fois en terme de réduction par animal et par unité de produit animal. Les voies d'approche les plus prometteuses pour réduire la production ruminale de CH$_4$ consisteraient à rechercher de nouveaux produits doués d'activité antiméthanogénique ou à favoriser la formation d'accepteurs d'électrons autres que CO$_2$ ou le formate, ou à agir dans le sens d'une réduction de la population de protozoaires. Enfin, cette réflexion globale sur la contribution des ruminants à l'effet de serre doit tenir compte du fait que ces animaux jouent un rôle essentiel dans l'équilibre de notre écosystème en transformant l'importante biomasse végétale mondiale en protéines animales (viande et lait principalement) qui constituent la base de l'alimentation humaine. Cet aspect doit contrebalancer les aspects négatifs liés à la production de méthane et à ses conséquences