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Ruminants are able to produce food for human consumption from plants, thanks to rumen bacteria. Bacteria are able to transform feed to microbial proteins and to biohydrogenate unsaturated fatty acids, contributing directly to fine milk composition. The database consists of daily records of milk yield, somatic cell score and 17 milk components such as fatty acids and proteins from 795 Lacaune dairy ewes. Ruminal samples were extracted from ewes using a gastric tube and sequenced to determine the bacterial composition by metabarcoding 16S rRNA gene on a next-generation sequencing platform. From bioinformatics analysis, 9,536,442 sequences were retained and re-grouped into 2,059 affiliated OTUs, represented by 751 to 168,617 sequences. Overall, 2,059 OTUs from 795 samples were attributed to 11 phyla. The most representative phyla were Bacteroidota (50.6%) and Firmicutes (43.6%), and the most abundant families were Prevotellaceae (37.9%), Lachnospiraceae (18.1%), Ruminococcaceae (8.97%). Both shared datasets will be useful for researchers to study the link between rumen bacteria and milk traits and to propose solutions to improve animal production and health.

Heating oils and oilseeds results in oxidized fatty acids with potential antimicrobial properties, that could affect digestive microbiota and therefore health. A long-term in vitro study was conducted to check the effects of one hydroperoxide, 13OOH cis-9,trans-11-C18:2 (13HPOD), and two aldehydes, hexanal and trans-2,trans-4-decadienal (T2T4D), on rumen bacteria and superoxide dismutase (SOD) activity. Rumen fluid was incubated with one of the three oxidation products for 54 h or 102 h. Controls without oxidation products were also incubated. Increasing incubation duration changed the bacterial community and caused acidification and probably oxidative stress, resulting in increased SOD activity. The bacterial community was highly affected by T2T4D, in particular the Bacteroidetes/Firmicutes ratio and the relative abundance of the Bacteroidales S24-7 group family, leading to an alteration of fermentation responsible for a higher final pH than those in control cultures and a diminution of SOD activity. Other oxidative products did not affect SOD activity, and hexanal did not modify the bacterial community compared to that of the control. The modification of the bacterial community by T2T4D represents a potential risk for the health of its host. Oxidative stress needs to be investigated in digestive ecosystems.

Using two successive types of diets (100% concentrate and 67% forage), this study explores the relationship between the ruminal microbiota of 78 Romane lambs and their feed efficiency (residual feed intake trait) or feeding behavior (feeding rate trait). Analysis was carried out phenotypically by correlating feed efficiency or feeding behavior traits with the relative abundance of bacteria at the phylum, family, and genus levels, and then genetically by comparing the microbiota of lambs selected for extreme breeding values for residual feed intake or feeding rate. Our results confirmed the major effect of diet on the ruminal microbiota composition. The microbiota of lambs consuming a forage-based diet was distinguished by higher microbial diversity and also by higher relative abundance of Firmicutes, whereas Bacteriodetes and Actinobacteria were relatively more abundant in the microbiota of lambs consuming a concentrate-based diet. Moreover, the comparison of lambs divergent for residual feed intake breeding values revealed that regardless of diet, more efficient lambs possessed a ruminal microbiota enriched in Coprococcus, Moryella, [Eubacterium] Brachy group, and [Eubacterium] hallii group, but depleted in Lachnospiraceae FD2005 and Shuttleworthia. The connection between microbiota composition and feeding rate was more tenuous, with no link between the abundance of particular genera and lambs genetically divergent for feeding rate.

Les ruminants, comme tous les mammifères, hébergent des billions de microbes symbiotiques, constituant les « microbiotes » de la peau, des voies digestives, respiratoires et génitales etc. La composition et les fonctions de ces microbiotes dépendent, entre autres, de leur habitat. L’utilisation des approches « -omiques », en particulier le séquençage de nouvelle génération, a permis de caractériser les organismes composant les microbiotes, leurs gènes et leurs activités. Les ruminants se distinguent par la présence dans leur rumen d'un microbiote spécialisé, composé principalement de bactéries, de protozoaires, d’archées et de champignons. Situé en amont des sites d'absorption, il joue un rôle central dans la nutrition des ruminants. La production des ruminants est particulièrement influencée par le microbiote intestinal (dont la population est diversifiée et spécifique du segment considéré) et le microbiote associé à la peau de la mamelle (réservoir important de la diversité microbienne du lait cru). Ces différents microbes interagissent entre eux et avec leur hôte sous l'influence de divers facteurs de variation, dont le principal est le régime alimentaire, mais aussi le milieu de vie et les pratiques d'élevage au début et milieu de la vie de l'animal. Des études récentes montrent un contrôle génétique potentiel par l'hôte de ses communautés microbiennes. En outre, il existe une accumulation de preuves des liens entre les microbiotes et la santé animale, l'efficacité de l'alimentation, les performances, la qualité des produits et la production de gaz à effet de serre. Ces constatations justifient l'intérêt croissant des éleveurs pour les microbiotes des animaux et leur modulation.

The growing expansion range of drug resistant parasitic nematode populations threatens the sustainability of ruminant farming worldwide. In this context, nutraceuticals, i.e. feed that would both fulfil dietary requirements while ensuring parasite control, would contribute to increase farming sustainability in developed and low resource settings. In this study, we characterized the anthelmintic potential of lupin seed extracts against major ruminant trichostrongylids, i.e. H. contortus and T. circumcincta. Our observations showed that total seed extracts from commercially available lupin varieties significantly inhibited larval migration. This anthelmintic effect was sustained on multidrug resistant field isolate and across parasite species and was mediated by the seed alkaloid content. Analytical chemistry revealed a set of four lupanine and sparteine-derivatives with anthelmintic activity and electrophysiology assays on recombinant nematode acetylcholine receptors suggested an antagonistic mode of action for lupin alkaloids. While commercial lupin seeds did not exert direct anthelmintic effect in H. contortus infected lupin-fed ewes and goats, it significantly dampened blood production losses suffered by goats. Lupin seed extracts hence provide a working basis for the development of novel anthelmintic compounds able to break drug resistance in the field, while they could be used to increase the resilience of infected dairy ruminants.

National audience; Selecting efficient animals is a major concern for livestock production, not only for economic but also for agro-environmental purposes. The selection of efficient animals leads to a decrease of feed intakes and limits pollutant emissions (greenhouse gases and nitrogen). In meat sheep, we demonstrated that Residual Feed Intake (CR) is a heritable selection criteria (h²=0.41) which is genetically correlated to average daily feed intake (rg=+0.73) under a concentrated diet. We setup a divergent selection experiment on CR (under a concentrated diet) in the Romane breed in order to 1) have a better understanding of biological processes underlying feed efficiency and 2) to evaluate the consequences of the genetic divergence on feed efficiency over a panel of traits (growth, fattening, muscular development,…), also when animals are fed with forages. After two generations of selection, the divergence is marked since it reaches 1.9 genetic standard deviations. Efficient animals (CR-) under a concentrated diet also have a lower daily feed intake with a forage-based diet (103 g less) than less efficient animals (CR+) while displaying similar growth. Significant differences between CR- and CR+ animals were also described at the level of the rumen microbiota.; La sélection d’animaux efficaces est un enjeu majeur pour les filières animales, que ce soit pour des raisons économiques, mais aussi agro-environnementales. En effet, sélectionner des animaux efficaces permet de limiter les quantités ingérées et les émissions de polluants (gaz à effet de serre et résidus azotés). Chez les ovins allaitants, nous avons montré que la consommation résiduelle (CR) est un critère de sélection héritable (h²=0,41) corrélé génétiquement à la quantité de concentré ingérée par jour (rg=+0,73). La mise en place de lignées divergentes sur la CR (mesurée avec une alimentation concentrée) en race Romane permet 1) de mieux comprendre les mécanismes biologiques impliqués dans l’efficacité alimentaire et 2) d’évaluer les conséquences de la sélection génétique de ce critère d’efficacité alimentaire sur une diversité d’autres caractères (croissance, engraissement, développement musculaire, …) mais aussi lorsque les animaux ont une ration fourragère. Après deux générations de sélection, la divergence est marquée puisqu’elle s’élève à 1,9 écart-type génétique. Nous avons montré que les animaux efficaces (CR-) avec une ration concentrée mangent également moins de fourrage (103 g en moins par jour par animal) que les animaux peu efficaces (CR+) tout en ayant des niveaux de croissance équivalents. Des différences significatives entre CR- et CR+ se retrouvent au niveau du microbiote ruminal

International audience; In the rumen, dietary polyunsaturated fatty acids (PUFA) are reduced by a multistage reaction called biohydrogenation (BH). BH leads to a high proportion of saturated fat in ruminant products, but also products some potential bioactive intermediates like conjugated linoleic and linolenic acids. BH is composed of two kinds of reactions: first an isomerization of PUFA followed by reductions (two for linoleic acid, C18:2n-6; three for alpha-linolenic acid, C18:3n-3). There is little knowledge about BH enzymes as BH bacterial species are the subject of a lot of studies. Nevertheless, both aspects must be explored to control BH and enhance the fatty acids profile of ruminant products. In the present study, an alternative approach was developed to study the enzymes produced in vivo by mixed ruminal bacteria, using inactivation of bacteria by chloramphenicol, an inhibitor of protein synthesis in prokaryotes, before in vitro incubation. To study C18:2n-6 and C18:3n-3 BH several experiments were used: (1) with different incubation durations (0 to 3) to estimate average rates and efficiencies of all BH reactions, and intermediates production; and (2) with different initial quantities of PUFA (0.25 to 2 mg) to estimate Michaelis-Menten enzymatic parameters, K-m and V-max. A last experiment explored the effect of pH buffer and donor cow diet on C18:2n-6 isomerization pathways. Concerning C18:2n-6 BH, this study confirmed the high saturability of its isomerization, the inhibition of both trans11 and trans10 pathways by a low pH, and the last reduction to stearic acid as the limiting-step. Concerning C18:3n-3, its BH was faster than C18:2n-6, in particular its isomerization (V-max = 3.4 vs. 0.6 mM/h, respectively), and the limiting-step was the second reduction to t11 -C18:1. Besides, our mixed isomerases had a higher affinity for C18:2n-6 than for C18:3n-3 (K-m = 2.0 x 10(-3) vs. 4.3 x 10(-3) M, respectively), but due to their high saturability by C18:2n-6, they had a lower efficiency to isomerize C18:2n-6 than C18:3n-3, Chloramphenicol-treated ruminal fluid would be a meaningful method to study the BH enzymes activities.

International audience; The ruminal microbiome plays a central role in the nutrition of the ruminant host, directly affecting production and undesirable by-products such as methane. Studies on ruminal microbiota highlight a significant effect of the host, but few publications have reported results concerning the impact of host genetics on microbial community composition. Rumen microbiota can be described using targeted or whole genome sequencing: rRNA is primarily used for the determination of taxonomic abundance of bacteria/archaea/fungi/protozoa, and a shotgun approach for abundance of genes in the rumen. An alternative high-throughput genotyping by sequencing technique was recently proposed by Hess et al. for describing microbial community composition in large numbers of animals. In sheep, a comparison of extreme animals (phenotypically or genetically) showed differences in their microbiota. Ellison et al. reported differences in bacteria and archea abundances in sheep having low or high residual feed intake, with some interactions with the diet. There was little evidence of links between feeding rate in sheep and ruminal bacteria abundances. From divergent lines, Kittelmann et al. showed 3 bacterial community types linked with genetic level of methane emission and de Barbieri et al. reported that selection for fleece weight is associated with differences in the diversity of ruminal bacteria. The first estimates of microbiota heritabilities in sheep were provided by Rowe et al. who reported genetic control of rumen microbial communities and genetic links to methane emissions. For this conference, Marie-Etancelin et al. estimated that ¼ of the taxa genera abundances in the rumen have a heritability greater than 0.1. It would be useful if these preliminary results on the targeted metagenome approach were followed up by whole gene quantification to characterize the functionality of microbiota. As in cattle, microbiota metagenome and host’s genome contributions to the variability of traits should be considered simultaneously in sheep experiments.

International audience; The microbiota of herbivorous animals plays a central role in the nutrition of its host, directly affecting his health and his ability to produce. Very few publications reported results concerning the impact of host genetics on the composition of ruminal microbiota. Thus, we proposed to study the genetic determinism of bacterial relative abundances of sheep rumen microbiota. 369 dairy Lacaune ewes raised indoor at the INRA Experimental Farm of La Fage, had a sampling of their rumen fluid done. These ewes were adult animals, fed with a 93% hay-silage based diet and belonged to 4 different lines (lines divergently selected on somatic cells count or on milk persistency). Ruminal metagenome were sequenced using 16s rRNA gene with Illumina Miseq technology. Bioinformatics analysis of the microbiota sequences were implemented with FROGS pipeline to obtain relative abundances of bacteria and R Phyloseq package to estimate biodiversity indices. Heritability estimates of the square root of relative abundances were computed in single trait using the VCE 6.0 software. FROGS pipeline allowed clustering the 4,944,307 informative sequences into 2,135 OTUs, which represented 247 bacteria taxas (140 genera, 50 families, 31 orders, 17 classes and 9 phyla). Significant differences between lines were observed: 4 bacteria generas have abundancies differences according to CCS lines (Olsenella, Prevotella 1, Prevotellaceaea Ga6a1, Syntrophococcus with always higher values for CCS+) and 4 others according to PERS lines (Coprococcus 1, Olsenella, Succonivibrionaceae U2, Syntrophococcus). At the genera scale, heritabilities estimates ranged from 0.00 to 0.49 with a standard error of 0.11 on average: 22% of genera had heritabilities higher than 0.1, which is lower than Estellé et al. on Large White (50% genera with h2>0.1). The most heritable genera (h2>0.25) were Ruminococcaceae UCG002, Lachnospira, Atopobium and Oscillospira which also were taxa with low abundances.

Gastrointestinal strongyles are a major threat to horses' health and welfare. Given that strongyles inhabit the same niche as the gut microbiota, they may interact with each other. These beneficial or detrimental interactions are unknown in horses and could partly explain contrasted susceptibility to infection between individuals. To address these questions, an experimental pasture trial with 20 worm-free female Welsh ponies (10 susceptible (S) and 10 resistant (R) to parasite infection) was implemented for five months. Fecal egg counts (FEC), hematological and biochemical data, body weight and gut microbiota composition were studied in each individual after 0, 24, 43, 92 and 132 grazing days.The predicted R ponies exhibited lower FEC after 92 and 132 grazing days, and showed higher levels of circulating monocytes and eosinophils, while S ponies developed lymphocytosis by the end of the trial. Although the overall microbiota diversity remained similar between the two groups, R and S ponies exhibited sustained differential abundances inClostridium XIVa, Ruminococcus, Acetivibrioand unclassifiedLachnospiraceaat day 0. These bacteria may hence contribute to the intrinsic pony resistance towards strongyle infection. Moreover,Paludibacter, Campylobacter, Bacillus, Pseudomonas, Clostridium III, Acetivibrio, members of the unclassifiedEubacteriaceaeandRuminococcaceaeand fungi loads were increased in infected S ponies, suggesting that strongyle and fungi may contribute to each other’s success in the ecological niche of the equine intestines. In contrast, butyrate-producing bacteria such asRuminococcus, Clostridium XIVaand members of theLachnospiraceaefamily decreased in S relative to R ponies. Additionally, these gut microbiota alterations induced changes in several immunological pathways in S ponies, including pathogen sensing, lipid metabolism, and activation of signal transduction that are critical for the regulation of immune system and energy homeostasis. These observations shed light on a putative implication of the gut microbiota in the intrinsic resistance to strongyle infection.Overall, this longitudinal study provides a foundation to better understand the mechanisms that underpin the relationship between host susceptibility to strongyle infection, immune response and gut microbiota under natural conditions in horses and should contribute to the development of novel biomarkers of strongyle susceptibility and provide additional control options.

International audience

International audience; Heating oil and oilseeds results in oxidation products that affect ruminal biohydrogenation of polyunsaturated fatty acids, altering milk fatty acids profile, and could be transferred to milk. An experiment was conducted to investigate the effects of oil heating on rumen and milk fatty acids profile and the transfer of oxidation products to milk. Sunflower oil was heated at 150 degrees C for 15 h and given to lactating dairy cows in a 2 x 2 arrangement: two groups of two cows, equipped with a ruminal cannula and receiving two diets (containing either heated or unheated oil) during two experimental periods. Oil heating generated hydroperoxides and/or hydroxyacids and aldehydes, in particular trans-2,trans-4-decadienal. In milk, heated oil only significantly decreased trans-11-C18:1 and cis-9,trans-11-CLA percentage compared to non-heated oil, and slightly increased cis-9, cis-12-C18:2 percentage, which was probably linked to an inhibition of the ruminal 12 isomerase by oxidative products in the rumen. However, feeding highly oxidized oil did not result in the appearance of hydroperoxides or hydroxyacids in milk and did not increase milk aldehydes content.

International audience; Although fat content in usual ruminant diets is very low, fat supplements can be given to farm ruminants to modulate rumen activity or the fatty acid (FA) profile of meat and milk. Unsaturated FAs, which are dominant in common fat sources for ruminants, have negative effects on microbial growth, especially protozoa and fibrolytic bacteria. In turn, the rumen microbiota detoxifies unsaturated FAs (UFAs) through a biohydrogenation (BH) process, transforming dietary UFAs with cis geometrical double-bonds into mainly trans UFAs and, finally, into saturated FAs. Culture studies have provided a large amount of data regarding bacterial species and strains that are affected by UFAs or involved in lipolysis or BH, with a major focus on the Butyrivibrio genus. More recent data using molecular approaches to rumen microbiota extend and challenge these data, but further research will be necessary to improve our understanding of fat and rumen microbiota interactions.

Consumption of milk and dairy products is important in Western industrialised countries. Fat content is an important constituent contributing to the nutritional quality of milk and dairy products. In order to improve the health of consumers, there is high interest in improving their fatty acid (FA) composition, which depends principally on rumen and mammary metabolism. This paper reviews the lipid metabolism in ruminants, with a particular focus on the production of trans and conjugated linoleic acids (CLA) and conjugated linolenic acids (CLnA) in the rumen. After the lipolysis of dietary lipids, an extensive biohydrogenation of unsaturated FA occurs by rumen bacteria, leading to numerous cis and trans isomers of 18:1, non-conjugated of 18:2, CLA and CLnA. The paper examines the different putative pathways of ruminal biohydrogenation of cis9-18:1, 18:2n-6, 18:3n-3 and long-chain FA and the bacteria implicated. Then mechanisms relative to the de novo mammary synthesis are presented. Ruminant diet is the main factor regulating the content and the composition of milk fat. Effects of nature of forage and lipid supplementation are analysed in cows and small ruminants species. Finally, the paper briefly presents the effects of these FA on animal models and human cell lines. We describe the properties of ruminant trans 18:1, when compared to industrial trans 18:1, CLA and CLnA on human health from meta-analyses of intervention studies and then explore the underlying mechanisms.

Milk and meat of ruminants have a specific fatty acid composition due to (i) extensive biohydrogenation processes in the rumen, which is the main site of feed digestion, (ii) de novo synthesis and partial desaturation of absorbed fatty acids in the mammary gland, and (iii) partial desaturation and elongation during meat fat synthesis. These processes result in low concentrations of polyunsaturated fatty acids, including limited amounts of conjugated fatty acids, and in significant amounts of trans monounsaturated fatty acids. Ruminant dairy and meat products are the only foods which naturally contain conjugated fatty acids. The main trans isomer is vaccenic acid (t11-18:1) of which the effects on human health cannot be confounded with those of other industrial trans isomers from hydrogenated oils. It is possible to modulate fatty acid composition of milk and meat from ruminants through animal feeding.

Dairy cow’s diet and milk fatty acids profile. Milk fatty acids profile is important for consumers, since milk and milk products provide a large part of fat in human diets and since dietary fatty acids profile influences human health. Milk fatty acids originate in part from the diet, and ruminal digestion strongly affects fatty acids profile. These physiological specificities must be taken into account to modulate milk fatty acids profile by modifying dairy cow’s diet. The main diet characteristics that can affect milk fatty acids profile are the choice of forage (pasture or stored forage) and fat supplementation, usually as oilseeds. This article underlines dietary choices that allow the control of unsaturated, n-3 or trans fatty acids., Le profil des acides gras du lait de vache est important pour le consommateur, le lait et les produits laitiers contribuant fortement aux apports de matières grasses, et le profil des acides gras alimentaires ayant un impact important sur la santé. Les acides gras du lait de vache proviennent seulement en partie de la ration, et la digestion ruminale modifie profondément le profil des acides gras de la ration. Ces particularités physiologiques conditionnent les stratégies permettant de moduler le profil des acides gras du lait en modifiant la ration des vaches. Les principaux choix alimentaires ayant un impact sur le profil des acides gras du lait sont le choix du fourrage (herbe ou fourrages conservés) et l’addition de matières grasses, le plus souvent sous forme de graines oléagineuses. Les choix alimentaires permettant de maîtriser les proportions d’acides gras insaturés, d’acides gras n-3 ou d’acides gras trans sont présentés dans cet article., Enjalbert Francis, Meynadier Annabelle. Alimentation des vaches laitières et composition en acides gras du lait. In: Bulletin de l'Académie Vétérinaire de France tome 169 n°3, 2016. pp. 171-175.

In dairy cows, several studies focused on the effects of sodium bicarbonate and fibre on ruminal linoleic acid (c9c12-C18:2) biohydrogenation (BH) whereas literature is scarce about the effect of live yeast, used as a feed additive. The objective of this in vivo study was to evaluate the capacity of two dietary feed additives, sodium bicarbonate and live yeast (Strain Sc47), and hay to modulate ruminal BH and particularly conjugated linoleic acids (CLA) and trans-monoenoic acids (t-C18:1) production. Four dry dairy cows fitted with ruminal cannula, were used in a 4×4 Latin square design. They were given a control diet (CD) at a daily feeding rate of 10.4 kg of dry matter/cow supplemented with 100 g/d of sodium bicarbonate or 5 g/d of live yeast or a hay diet formulated to provide the same main fatty acids (FA) as CD during a 14-d experimental period. Ruminal pH and redox potential were measured from 1 h before feeding to 8 h after, and ruminal fluid samples were taken at 5 h after feeding for volatile fatty acid, ammonia and fatty acid determination. In addition to the in vivo experiment, an in vitro experiment was carried out to ascertain the possible mode of action of live yeast on c9c12-C18:2 BH: ruminal fluid was obtained from a donor cow fed with hay and was incubated in batch cultures over 6 h with a 6-pH buffer using starch, urea and grape seed oil as substrates. Results gathered from both experiments suggested that live yeast supplement increased the accumulation of t-C18:1 compared to sodium bicarbonate and prevented the formation of C18:0 which is usually observed when hay is added to a high concentrate diet. The accumulation of t-C18:1 observed in presence of live yeast was probably due to an inhibition of the second reduction step as a result of a more efficient isomerisation of c9c12-C18:2., Chez les vaches laitières, plusieurs études montrent les effets du bicarbonate de sodium et des fibres sur la biohydrogénation (BH) de l'acide linoléique (c9c12-C18 :2) dans le rumen alors qu'elles sont rares en ce qui concerne ceux de la levure vivante, utilisée comme additif dans l'alimentation. L'objectif de cette étude conduite in vivo était d'évaluer les capacités de deux additifs alimentaires, le bicarbonate de sodium et la levure vivante (souche Sc 47), ainsi que du foin, à moduler la BH ruminale et en particulier la production d'acides linoléiques conjugués (CLA) et d’acides trans-monoenoiques (t-C18:1). Quatre vaches laitières taries, munies d'une canule ruminale, ont été utilisées dans un carré latin 4 × 4. Elles ont reçu individuellement environ 10,4 kg de matière sèche (MS)/j d’un régime témoin (CD) additionné de 100 g/j de bicarbonate de sodium ou de 5 g/j de levures vivantes, ou un régime alimentaire contenant du foin grossier formulé pour offrir des teneurs en acides gras (AG) identiques à celles fournies par CD, pendant une période expérimentale de 14 jours. Le pH et le potentiel redox du rumen ont été mesurés à partir de 1 h avant le repas jusqu’à 8 h après, et des échantillons de contenu ruminal liquide ont été prélevés 5 h après le repas pour le dosage des concentrations en acides gras volatils, en ammoniac et des teneurs en acides gras. En outre, en parallèle de l'expérience in vivo, une expérience in vitro a été réalisée pour préciser les voies d’action des levures vivantes sur la BH du c9c12-C18:2 sous conditions contrôlées : le contenu ruminal a été prélevé sur des vaches donneuses nourries au foin et incubé pendant 6 h en milieu tamponné à pH 6 en utilisant comme substrats de l'amidon, de l'urée et de l'huile de pépins de raisin. L’analyse combinée des résultats des deux expériences suggère que les levures vivantes ont induit une accumulation plus importante de t-C18:1 que le bicarbonate de sodium et qu’elles ont freiné la formation de C18:0 habituellement observée lors de l’ajout de foin dans un régime riche en concentrés. L’accumulation de t- C18:1 en présence de levures vivantes serait probablement due à l’inhibition de la seconde réduction induite par une meilleure efficacité de l’isomérisation de c9c12-C18:2.

International audience; Feed efficiency is one of the keystones that could help make animal production less costly and more environmentally friendly. Residual feed intake (RFI) is a widely used criterion to measure feed efficiency by regressing intake on the main energy sinks. We investigated rumen and plasma metabolomic data on Romane male lambs that had been genetically selected for either feed efficiency (line rfi−) or inefficiency (line rfi+). These investigations were conducted both during the growth phase under a 100% concentrate diet and later on under a mixed diet to identify differential metabolite expression and to link it to biological phenomena that could explain differences in feed efficiency. Nuclear magnetic resonance (NMR) data were analyzed using partial least squares discriminant analysis (PLS-DA), and correlations between metabolites’ relative concentrations were estimated to identify relationships between them. High levels of plasma citrate and malate were associated with genetically efficient animals, while high levels of amino acids such as L-threonine, L-serine, and L-leucine as well as beta-hydroxyisovalerate were associated with genetically inefficient animals under both diets. The two divergent lines could not be discriminated using rumen metabolites. Based on phenotypic residual feed intake (RFI), efficient and inefficient animals were discriminated using plasma metabolites determined under a 100% concentrate diet, but no discrimination was observed with plasma metabolites under a mixed diet or with rumen metabolites regardless of diet. Plasma amino acids, citrate, and malate were the most discriminant metabolites, suggesting that protein turnover and the mitochondrial production of energy could be the main phenomena that differ between efficient and inefficient Romane lambs.

Master