Post-weaning maturation of rabbit caecal microbial communities: impact of live yeast intake

International audienceThe aims of this work were first to evaluate nutritional requirements of early weaned kits (23 days of age), more especially fibre (experiment 1) and protein (experiment 2) needs. In experiment 1, 276 early weaned rabbits were offered from 23 to 50 days of age one of the three experimental diets containing increasing acid-detergent fibre level (160, 190 or 220g/kg). Fibre was substituted by starch and fat to obtain three isoenergetic diets. In experiment 2, 306 early weaned rabbits were offered from 23 to 50 days of age one of the three experimental diets containing increasing crude protein (CP) level (150, 180 or 210g/kg). Protein was substituted by starch and fat to obtain three isoenergetic diets. These studies revealed no effect of the dietary fibre level and the dietary CP level on health status. But from 23 to 36 days of age rabbits given diets containing a fibre level over 190g/kg or a CP level under 180g/kg showed the lowest growth rate as compared with other respective treatments. Secondly, this research aimed to evaluate the interaction between age at weaning (23 days or 35 days of age) and food (RD and RY diets) on digestive health and performances of young rabbits (experiment 3). RD diet was formulated to contain (per kg) 170g starch, 160g fibre and 180g CP (according to the nutritional requirements of does) and RY diet was formulated to reach 110g starch, 160g fibre and 210g CP (according to the results of experiments 1 and 2). 39 litters of nine pups per litter were assigned at 18 days of age to one of four experimental groups in a 2×2 factorial design: RD23 (no. =84 rabbits), RY23 (no. =85 rabbits), RD35 (no. =86 rabbits) and RY35 (no. =74 rabbits). Food intake and live weight were not influenced by feeding strategy. Between 23 and 35 days of age, mortality was higher in RY than in RD group (20·4 v. 6·8% respectively; P<0·05). During this period growth rate was proportionately 0·584 higher in conventionally weaned than in early weaned rabbits (P<0·001). After 35 days of age, food intake and growth rate were proportionately 0·104 and 0·097 higher respectively in conventionally than in early weaned rabbits (P<0·05). Consequently, live weight was higher in conventionally weaned rabbits at both 35 and 53 days of age (proportionately +0·113 and +0·267 respectively; P<0·001). Mortality rate between 23 and 35 days was 21 points higher (P<0·001) in early weaned than in conventionally weaned pups and 43 points higher (P<0·001) from 35 to 53 days of age. These data suggest that the removal of milk feeding by early weaning leads to detrimental effects on health and growth of the young, which were not compensated by a diet meeting better their nutritional needs

Temporal effect of exogenous organic inputs on soil microbial communities under conservation agriculture

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Relationship between initial soil microbial diversity and the quality of exogenous organic matter: Effect on carbon stability of Soil Organic Matter

International audienceIn a context of global climate change, carbon management is an important point. Therefore, the strategy of sequestration of stable carbon in agricultural soils is the preferred option to offset emissions of greenhouse gases. In addition, from an agronomic point of view, changing agricultural practices by Exogenous Organic Matter (EOM) inputs, allows to significantly increase the organic carbon storage in soils.The objectives of our work were to understand: i) the respective relationship between the chemical composition of Organic Waste Products (OWP) and the diversity of soil microbial communities, and ii) the effect of those communities on the degradation of organic matter.This study concentrated mainly on four organic waste products: green waste compost, green waste-sludge compost, sewage sludge and cattle manure mature. The degradation of these OWP was studied by incubation at 20°C for 6 months, in two agricultural soils that have different microbial diversity status (Permanent Grassland PG, Arable Cropping AC). The OWP were made at constant carbon (4g carbon/kg dry soil).The physicochemical characterization of the organic matter of OWP and the soils was conducted to determine the total carbon and total nitrogen. Furthermore, thermal analysis has been proposed in order to assess their level of stability. Soil functional activity was measured through i) enzymatic activities including cellulase, xylanase, lipase, and alkaline phosphatase and ii) potential metabolic activity of heterotrophic bacteria with BiologTM ecoplate well system (average well color development (AWCD) and Richness (R)). In parallel, the dynamic of carbon mineralization was followed.Thermogravimetric analysis showed different levels of stability between OWP. Indeed, the weight losses between 200 and 760°C was higher in order of importance, for the sewage sludge, green waste-sludge compost, cattle manure and green waste compost. These weight losses occurred mainly in two steps. At 210–320°C range, the peak observed was attributed to the combustion of carbohydrates, which were more important for sewage sludge (41%), even though the thermal degradation of the aromatic structures occurred at 400–679°C for green waste compost (16%). Moreover, the combination of these two results seemed to indicate that organic matter is slightly more transformed in the first case than in the second. These results are in agreement with those obtained on the Van Soest biochemical fractionation of OWP, and with Organic Matter Stability Index (OMSI).Preliminary results during the first 21 days of incubation indicated changes in microbial functions depending on the time of incubation, the nature of OWP and the initial status of microbial diversity of soils. Indeed, the monitoring of the measured variables often indicated significant changes at 8 and 14 days of incubation. Moreover, the microbial community from PG soil was more active than from AC one, if we consider the functional activities or the carbon mineralization. Finally, adding OWP favored carbon mineralization in both soils. However, the effects on microbial functions were more nuanced. In fact, in PG soils, the EOM input did not change functional activities. In contrast, in AC modality, the metabolic activity was generally higher when OWP were added. However, the enzymatic activities were not stimulated by inputs. Green waste-sludge compost was hardly degraded by cultivable bacteria. We found that the metabolic activity (R, AWCD) was low and equivalent to the AC soil. The same result was observed with the dynamic of carbon mineralization.In summary, the first results of this study show that depending on the composition of the microbial communities of both soils and composition of the OWP, microbial activities seem to respond differently and more significantly for the AC soil and for stable OWP. To complete our study, it is necessary to conduct additional measurements on microbial community such as abundance (total DNA, carbon biomass) and diversity (bacterial and fungal DNAs) up to 6 months of soil incubation

Thermogravimetry and FT-IR spectroscopy: efficient approaches for organic amendments stability analysis?

International audienceFaced with the need to reduce the use of chemical fertilizers, spreading of exogenous organic material (EOM) provides nutrients for crops and improving soil fertility depending on their biochemical composition. Our aim was to study the biochemical composition of EOM according to different methods, to predict their behavior in soil and determine appropriate management of these EOM.Six organic amendments (urban sludge, household compost, poultry manure, sludge compost, dry digestat, mature cattle manure) were characterized according their i) thermal decomposition by thermogravimetric analysis (TG-DSC) in oxidizing atmosphere between 23-900◦C, and by stability index R1 (% Masse loss of aromatic peak/% Masse loss of aliphatic peak) (ii) biological stability, IROC indicator [1], based on Van Soest biochemical fractionation [2] and short-term carbon mineralization in soil [3] and iii) FT-IR spectroscopy (wave number range 4000–400 cm-1).The six EOM present different TG weight loss curves (WL%). Total WL of organic matter fraction ranged from 40% (sludge compost) to 72% (poultry manure). The first derivative of the TG trace (DTG) profile clearly differentiated two exothermal peaks: 268-300°C and 441-497°C which respectively, could be attributed to carbohydrates (cellulose and lignocellulosic) and recalcitrant (complex aromatic) compounds decomposition. The R1 index showed a good sensitivity in detecting the changes in the forms of carbon composition. Urban sludge, household compost and poultry manure were more biodegradable (R1<0.8) and have low lignin content, contrary to sludge compost, dry digestat and mature cattle manure which were thermally more stable with a having 2 times more of lignin content. These results were globally consistent with values of IROC. The FT-IR spectra also allows to discriminate the different EOM. These results indicate that thermogravimetric and FT-IR spectra analysis are consistent with the IROC indicator that could be consider as reference but the techniques are much more easier to set up. As a perspective, these approach could be compared with sequential chemical extractions coupling with 3D fluorescence spectroscopy.[1] Lashermes, G., Nicolardot, B., Parnaudeau, V., Thuriès, L., Chaussod, R., Guillotin, M.L., Linères, M., Mary, B., Metzger, L., Morvan, T., Tricaud, A., Villette, C., Houot, S. 2009. European Journal of Soil Science, 60, 297-310.[2] AFNOR, 2009. Norme XPU 44-162. AFNOR, Paris[3] AFNOR, 2009. Norme XPU 44-163. AFNOR. Paris

Impact of diverse soil microbial communities on crop residues decomposition

International audienceSoils provide many basic ecosystem services for our society and most of these services are carried out by the soil communities, thus influencing soils quality. Soil organic matter (SOM) can be considered as one of the most important soil quality indices for it plays a determinant role in many physical, chemical and biological processes, such as soil structure and erosion resistance, cation exchange capacity, nutrient cycling and biological activity (Andrews et al., 2004). Since a long time, exogenous organic inputs are largely used for improving agricultural soils, affecting highly soil fertility and productivity. The use of organic amendments such as crop residues influences the soil microbial populations' diversity and abundance. In the meantime, soil microbial communities play a major role in the organic matter degradation, and the effect of different microbial communities on the decomposition of crop residues is not well documented. In this context, studying the impact of crop residues on soil microbial ecology and the processes controlling the fate of plant residues in different management practices is essential for understanding the long-term environmental and agronomic effects on soil and organic matters. Our purpose in the present work was to investigate the decomposition by two contrasting microbial communities of three crop residues, and compare the effect of different residues amendments on the abundance and function of each soil microbial communities. Among the main crops which produce large amounts of residues, we focused on three different plants: wheat (Triticum aestivum L.), rape (Brassica napus) and sunflower (Helianthus annuus). The residues degradation in two soils of different management practices and the microbial activity were evaluated by: microbial abundance (microbial carbon, culturable bacteria, total DNA, qPCR), in combination with functional indicators (enzymatic assays and Biolog substrate utilization), kinetics of C and N mineralization, and chemical measures. Physicochemical composition of crop residues was assessed by Fourier transform infrared spectroscopy FTIR technique at 0 and 83 days. The experiment was conducted in microcosms over 83 days for the biological measurements and 175 days for the C mineralization. The first results showed variations in the C & N rates, and the microbial abundances and functions over time, with a peak at 5 days and a decrease at 83 days for most of the measurements. The soil microbial communities' composition (different management practices) highly impacted the crop residues decomposition. The biochemical composition of crop residues influenced less the microbial communities of each soil. Further studies on the valorization of these residues into agro materials will be carried out. References: Andrews SS., Karlen DL., and Cambardella CA. (2004) The soil management assessment framework: a quantitative soil quality evaluation method. Soil Science Society of America, 68: 1945-196

Guide d’interprétation à l’analyse des bioindicateurs Microbioterre : un nouvel outil pour un diagnostic de la fertilité à la parcelle

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Microbioterre: study of the relationships between indicators of soil status and C & N functions in different agricultural practices (meta-analyses).

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Guide d’interprétation à l’analyse des bioindicateurs Microbioterre : un nouvel outil pour un diagnostic de la fertilité à la parcelle

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Microbioterre : intégrer des indicateurs de microbiologie dans l’analyse de terre pour améliorer la gestion des restitutions organiques

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Mise en place d’un outil de diagnostic d’état des sols agricoles en systèmes de grandes cultures et polycultures élevage

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