A milk urea model to better assess nitrogen excretion and feeding practice in dairy systems

A milk urea model to better assess nitrogen excretion and feeding practice in dairy systems. 20. Nitrogen Worksho

Emissions d’ammoniac et de protoxyde d’azote au bâtiment et au stockage de fumiers bovins

Emissions d’ammoniac et de protoxyde d’azote au bâtiment et au stockage de fumiers bovins. Colloque Apivale - Produits résiduaires organiques : ingrédients clés de la bioéconomie circulair

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

ELFE, a database to determine greenhouse gases and ammonia emissions factors from livestock

ELFE, a database to determine greenhouse gases and ammonia emissions factors from livestock. 20. Nitrogen Workshop. Coupling C-N-P-S cycle

Identification of rumen microbial biomarkers linked to methane emission in Holstein dairy cows

Mitigation of greenhouse gas emissions is relevant for reducing the environmental impact of ruminant production. In this study, the rumen microbiome from Holstein cows was characterized through a combination of 16S rRNA gene and shotgun metagenomic sequencing. Methane production (CH4) and dry matter intake (DMI) were individually measured over 4–6 weeks to calculate the CH4 yield (CH4y = CH4/DMI) per cow. We implemented a combination of clustering, multivariate and mixed model analyses to identify a set of operational taxonomic unit (OTU) jointly associated with CH4y and the structure of ruminal microbial communities. Three ruminotype clusters (R1, R2 and R3) were identified, and R2 was associated with higher CH4y. The taxonomic composition on R2 had lower abundance of Succinivibrionaceae and Methanosphaera, and higher abundance of Ruminococcaceae, Christensenellaceae and Lachnospiraceae. Metagenomic data confirmed the lower abundance of Succinivibrionaceae and Methanosphaera in R2 and identified genera (Fibrobacter and unclassified Bacteroidales) not highlighted by metataxonomic analysis. In addition, the functional metagenomic analysis revealed that samples classified in cluster R2 were overrepresented by genes coding for KEGG modules associated with methanogenesis, including a significant relative abundance of the methyl‐coenzyme M reductase enzyme. Based on the cluster assignment, we applied a sparse partial least‐squares discriminant analysis at the taxonomic and functional levels. In addition, we implemented a sPLS regression model using the phenotypic variation of CH4y. By combining these two approaches, we identified 86 discriminant bacterial OTUs, notably including families linked to CH4 emission such as Succinivibrionaceae, Ruminococcaceae, Christensenellaceae, Lachnospiraceae and Rikenellaceae. These selected OTUs explained 24% of the CH4y phenotypic variance, whereas the host genome contribution was ~14%. In summary, we identified rumen microbial biomarkers associated with the methane production of dairy cows; these biomarkers could be used for targeted methane‐reduction selection programmes in the dairy cattle industry provided they are heritable.info:eu-repo/semantics/publishedVersio

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

DETERMINANTS DE L'UTILISATION DES RESSOURCES ALIMENTAIRES PAR LE CHEVAL : INFLUENCE DE LA QUALITE ET DE LA HAUTEUR DE LA VEGETATION SUR L'INGESTION ET LES CHOIX DE SITES D'ALIMENTATION

Diplôme : Dr. d'UniversitéThe characteristics of resources are important determinants of intake and patch selection by herbivores, whatever the time scale considered. In this thesis we have used horses to explore the adaptations of a large herbivore faced with variations in their resource quantity and/or quality, using an experimental approach. From the meta-analysis of individual measures of intake on a large range of hay quality, we have shown that the horses were able to compensate for the low nutritional value of their food by eating more. However, the animals expressed different responses to a decrease in forage quality and we discuss this individual variability in terms of behavioural strategies. In choice situations at pasture, when the animals could adjust their feeding behaviour between alternative patches differing in height only or in height and quality simultaneously, intake levels were maintained (13gDDM/kgLW/day), whatever the amount of grass offered. Instantaneous intake rates increased with grass height but the average daily intake rates achieved on the different swards types on a daily basis were constant, perhaps because depletion over the day levelled the instantaneous intake rates. From both studies at trough and at pasture, the horses were able to maintain their intake levels when energy and nitrogen content of the resource declined in order to satisfy their nutritional requirements. In a choice situation between feeding patches that did not differ much in quality, the horses selected the taller swards where they achieved higher DM and digestible DM intake rates (as predicted by optimal foraging theory). When the preferred sward matured, and a trade-off between sward height and quality was deepened, the horses increased their feeding time on the shorter good quality alternative, even though digestible DM intake rates were still higher on the reproductive sward. We demonstrate that, in both studies at pasture, the maximisation of their digestible crude protein intake rate explains the selection of their feeding sites. As protein supplies on the mature swards became limiting, the animals favoured the quality of their diet and selected the patches that met their nutritional requirements. The horses expressed partial preferences leading to sub-optimal choices: they did not graze the most profitable sward only. They may have done so to re-evaluate sward value regularly, as nutrient intake rate varies due to depletion by the animals. In the last study at pasture, when grass height and quality differed simultaneously, the sward maximising protein content was not the one that maximised energy content, and we propose that by feeding on both sward types they probably balanced their protein and energy intake. By modulating their feeding time between the different feeding sites, the horses adapted their behaviour to the heterogeneity of their environment and achieved a high-quality, balanced diet that met their nutritional requirements. Some prospects for further research are proposed in order to improve the management of horses and their pastures. Finally, the contributions of this work to the understanding of the relationships between large herbivores and their resources are discussed.Les caractéristiques de la ressource occupent une place prépondérante à toutes les étapes des processus d'ingestion et de sélection alimentaire par les herbivores, à court et à long terme. Par une approche expérimentale, nous avons contribué à une meilleure compréhension des adaptations mises en place par les chevaux confrontés à des variations de la qualité et de la hauteur de la végétation offerte. A partir de l'analyse de données individuelles d'ingestion mesurées à l'auge pour une large gamme de fourrages, nous avons montré que les chevaux pouvaient compenser dans une certaine mesure une faible valeur nutritive du fourrage par une augmentation du niveau d'ingestion. Tous les individus n'ont pourtant pas exprimé la même réponse face à la diminution de la qualité de leur ressource. A partir de deux expériences conduites au pâturage, nous avons montré que lorsque les chevaux avaient le choix d'ajuster leur temps d'alimentation entre deux couverts variant uniquement en hauteur, ou simultanément en hauteur et en qualité, ils pouvaient maintenir un niveau d'ingestion de MSD relativement constant. Bien que la vitesse d'ingestion instantanée de MS digestible ait été plus élevée sur les couverts les plus accessibles, la déplétion des couverts au cours de la journée a probablement nivelé les vitesses d'ingestion moyennes réalisées sur l'ensemble des couverts, ce qui pourrait expliquer, au moins en partie, la constance des quantités ingérées journalières de MS digestible. Les résultats obtenus au pâturage et à l'auge s'inscrivent dans une relation générale montrant que lorsque la concentration en énergie et en azote de la ressource diminue, les chevaux peuvent maintenir leur niveau d'ingestion de façon à couvrir leurs besoins alimentaires. En situation de choix binaire entre des sites d'alimentation dont la qualité était proche, les chevaux ont pâturé préférentiellement les couverts les plus hauts sur lesquels ils ont maximisé leurs vitesse d'ingestion de MS et de MS digestible (en accord avec les théories d'optimisation). À mesure que le couvert le plus haut est devenu mature, et donc que le compromis entre la qualité et la hauteur de la ressource est devenu important, les chevaux ont reporté leur temps d'alimentation sur les couverts les plus courts de meilleure qualité, bien que la vitesse d'ingestion de MS digestible soit restée plus élevée sur le couvert le plus haut. Nous avons montré que ce comportement est en relation avec la nécessité de satisfaire les besoins azotés, le choix des sites sélectionnés par les animaux pouvant s'expliquer par la vitesse d'ingestion instantanée de matières azotées digestibles permise par les couverts végétaux. Au cours de la journée, les chevaux n'ont pour autant pas exprimé des choix strictement optimaux, ne pâturant pas exclusivement le couvert le plus profitable. Dans l'étude où hauteur et qualité de l'herbe ont varié simultanément, le partage du temps d'alimentation entre les différents sites a probablement permis d'équilibrer leur régime sur la base de l'azote et de l'énergie. Par la modulation de leur temps de pâturage sur les différents sites d'alimentation, les chevaux ont été capables d'adapter leur comportement à l'hétérogénéité de leur environnement, afin de maintenir un régime de bonne qualité et de satisfaire leurs besoins nutritionnels. Quelques perspectives de recherche sont proposées afin d'aboutir à des recommandations en terme de gestion de l'alimentation de ces herbivores et des prairies pâturées. Enfin, nous concluons sur la contribution de cette thèse à la compréhension des relations entre grands herbivores et ressources végétales