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Growing world population and depletion of fossil resources have led to an increasing food and energy demand. While oleaginous plants are mostly cultivated for their fruits or their seeds in food industry, they are also valued in as an alternative to petrochemicals (biolubricant, biofuels). The production of lipids and unusual fatty acids increased the interest for unicellular organisms: yeasts. The aim of this work is to study two biological models: flax seed (Linum usitatissimum), whose oil is made up of 57% omega-3, and yeast Yarrowia lipolytica, exploited as a biotechnological chassis. The approach used to understand lipid metabolism is fluxomics. In addition, the development of a predictive model based on isotopic labelling (MFA) or constraint-based one (FBA) allows a dynamic analysis of the metabolism. The comparative study of three flax lines (with different oil and omega-3 levels) provided a better understanding of the mechanisms leading to lipid accumulation (up to 44.2 g.100 gDW-1). Therefore, we have been able to show that sucrose assimilation and starch remobilization are essential for fatty acid precursors and cofactors synthesis. Strong involvements of cytosolic glycolysis (G3P, acetyl-CoA) and pentose phosphate pathway (NADPH) have been noted, while protein and cell wall synthesis are limiting steps. In addition, PDAT would be a central enzyme for the incorporation of PUFA into TAGs. The study of three Yarrowia lipolytica strains also helped us to better understand yeast metabolism. The assimilation of an alternative carbone source to glucose, glycerol, led to a major metabolic redirection towards gluconeogenesis. The TAG synthesis flux especially uses glycolysis and a part of TCA cycle to convert citrate into acetyl-CoA. Kennedy pathway optimizations (GPD1 and DGA2 gene overexpression) allowed a lipid content improvement: +72% compared to a strain optimized for the synthesis of unusual fatty acids (LRO1 gene expression, encoding for a PDAT enzyme). The main competitive pathways are carbohydrate synthesis (glycogen) and citrate secretion (here repressed thanks to slow glucose assimilation. PDAT (LRO1 gene) also led to unusual fatty acid accumulation.; Une population mondiale croissante et l’épuisement des ressources fossiles a conduit à une augmentation de la demande alimentaire et énergétique. Si les plantes oléagineuses sont majoritairement exploitées pour leurs fruits et leurs graines riches en huiles dans le secteur agroalimentaire, elles sont également valorisées comme alternative aux produits pétrosourcés (biolubrifiants, biocarburants). La production de lipides et d’acides gras inhabituels a rapidement suscité un intérêt envers les organismes unicellulaires : les levures. L’objectif de ce travail consiste à étudier deux modèles biologiques : la graine de lin (Linum usitatissimum), dont l’huile est constituée à 57% d’oméga-3, et la levure oléagineuse Yarrowia lipolytica, exploitée comme châssis biotechnologique. L’approche utilisée pour appréhender le métabolisme lipidique est la fluxomique. De plus, la conception d’un modèle prédictif reposant sur un marquage isotopique (MFA) ou la contrainte (FBA) permet une analyse dynamique du métabolisme. L’étude comparative de trois lignées de lin (teneurs en huile et oméga-3 différentes) a permis une meilleure compréhension des mécanismes menant à l’accumulation des lipides (jusqu’à 44,2 g.100g-1 MS). Ainsi, nous avons pu montrer que l’assimilation du saccharose et la remobilisation de l’amidon sont essentiels à la synthèse des précurseurs et du NADPH nécessaires à la synthèse des AG. Une forte implication de la glycolyse cytosolique et de la voie des pentoses phosphate plastidiale a pu être notée, tandis que la synthèse des protéines et de la paroi cellulaire a été une étape plutôt limitante. De plus, la PDAT semblerait être une enzyme essentielle à l’incorporation d’acides gras polyinsaturés dans les TAG. L’étude de trois souches de Yarrowia lipolytica a également permis d’appréhender le métabolisme de la levure. L’assimilation d’une source de carbone alternative au glucose (glycérol) a entraîné une redirection métabolique majeure vers la néoglucogénèse. Le flux majoritaire pour la synthèse des TAG emprunte la glycolyse et une partie du cycle de Krebs, afin de convertir le citrate en acétyl-CoA. L’optimisation de la voie Kennedy (GPD1 et DGA2) a permis une amélioration du contenu en lipides : +72% par rapport à une souche optimisée pour la synthèse des acides gras inhabituels (expression du gène LRO1, codant pour une PDAT). Les principales voies compétitives sont la synthèse de glucides de réserve et la sécrétion de citrate, réprimée ici grâce à une assimilation de glucose modérée. La PDAT est là encore impliquée dans l’accumulation des acides gras inhabituels.

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Dietary supplementation with linseed, saponins and nitrate is a promising methane mitigation strategy in ruminant production. The main objective of this work was to assess the effects of these additives on the rumen microbiota in order to understand underlying microbial mechanisms of methane abatement. Two 2 × 2 factorial design studies were conducted simultaneously, which also allowed us to make a broad-based assessment of microbial responses. Eight non-lactating cows were fed diets supplemented with linseed or saponin in order to decrease hydrogen production and nitrate to deviate hydrogen consumption; also, combinations of linseed plus nitrate or saponin plus nitrate were used to explore the interaction between dietary treatments. Amplicon sequencing of 18S and 16S rRNA genes was employed to characterise rumen microbes. Nitrate fed alone or in combination in both studies dramatically affected the composition and structure of rumen microbiota, though impacts were more evident in one of the studies. Linseed moderately modified bacterial community structure with no effect on rumen methanogens and protozoa. Indicator OTU analysis revealed that both linseed and nitrate reduced the relative abundance of hydrogen-producingRuminococcaceae. Linseed increased the proportion of bacteria known to reduce succinate to propionate, whereas nitrate supplementation increased nitrate-reducing bacteria and decreased the metabolic activity of rumen methanogens. Saponins had no effect on the microbiota. Inconsistency found between the two studies, when nitrate was fed to the cows could be explained by changes in microbial ecosystem functioning rather than changes in microbial community structure.ImportanceThis study aimed at identifying the microbial mechanisms of enteric methane mitigation when linseed, nitrate and saponins were fed to non-lactating cows alone or in a combination. Hydrogen is a limiting factor in rumen methanogenesis. We hypothesised that linseed and saponins would affect hydrogen producers and nitrate would deviate hydrogen consumption thus leading to reduced methane production in the rumen. Contrary to what was foreseen, both linseed and nitrate had a deleterious effect on hydrogen producers; linseed also redirected hydrogen consumption towards propionate production, whereas nitrate stimulated the growth of nitrate reducing and hence hydrogen-consuming bacterial taxa. Fundamental knowledge of microbial mechanism involved in rumen methanogenesis, provides novel insights for the development of new or the optimisation of existing methane mitigation strategies.

During two months, sixty Pietrain × (Landrace × Large White) finishing pigs (50.7 to 115.2 kg live weight) received diets containing various levels of C18:3n-3 from linseed and C22:6n-3 from Schizochytrium microalgae to increase the content of these fatty acids (FA) in their lean and fat tissues. Samples of tissues have been extracted from the carcass at the slaughterhouse. Tissues of pigs fed linseed had the highest C18:3n-3 and C20:3n-3 contents, while the C20:4, C20:5 and C22:6n-3 contents increased in tissues with microalgae diets. Diaphragm was fatter, but contained less monounsaturated FA, total n-6 and n-3 polyunsaturated FA (PUFA) than longissimus thoracis et lumborum and semimembranosus muscles due to their different roles. The leaf fat was the most saturated and monounsaturated tissue, regardless of the diet. Adipose tissues located in extremities contained more n-3 and n-6 PUFA than adipose tissues located in the middle of the carcass. This study showed the existence of a PUFA gradient depending on tissue location.

La qualité nutritionnelle des produits animaux dépend de la composition des matières premières de l’aliment de l’animal. La fraction lipidique est particulièrement importante pour orienter les dépôts d’acides gras des produits animaux. Une filière s’est mise en place avec utilisation de graines de lin riches en acides gras n-3 (ou oméga 3) dans l’alimentation animale pour améliorer les lipides des produits animaux et ainsi répondre aux besoins de l’homme. La faisabilité technique et économique a été montrée ainsi que l’intérêt pour la santé de l’homme., Breeding factors and diet influence the quality of animal products. There is a direct relationship between the nature of the fatty acids in feed and those which are deposited in the animal products. A sector has been set up with the use of flax seeds rich in n-3 (or omega 3) fatty acids in animal feed to improve the lipids of animal products and thus meet the needs of humans. The technical and economic feasibility has been demonstrated as well as the interest in human health.

Secoisolariciresinol (SECO) is a natural antioxidant lignan accumulated in large amounts in the seedcoat of flax and retained in the flaxseed cake residue during linseed oil pressing. Here SECO was extracted and purified from flaxseed cake and assayed for its ability to prevent oxidation of linseed oil and an o/w emulsion containing linseed oil. For this purpose, an accelerated storage (Schaal oven) test was performed and SECO effectiveness was compared to that of two antioxidants commonly used in food and cosmetic products: α-tocopherol (α-TOCO) and butylated hydroxyanisole (BHA). In our hands, SECO addition, ranging from 50 to 500 μmole per kg oil, significantly decreased the production of both primary (conjugated dienes, CD) and secondary (thiobarbituric acid-reactive substances, TBARS) oxidation products. This study evidenced that SECO is an effective stabilizer of linseed oil and its o/w emulsion and this protective effect outperformed both the natural α-TOCO and the synthetic BHA antioxidants. In particular, SECO was the most effective in the protection of the o/w emulsion against secondary oxidation products, which makes it a potential alternative preservative for oily products in foods and cosmetics. Practical applications: The present study could lead to applications in the food and cosmetic industries for the stabilization of o/w emulsions. Addition of SECO to linseed oil, already rich in ω-3, could also result in a new functional food with synergistic beneficial actions on human health.

International audience; Effects of fatty acids of linseed in different forms, on ruminal fermentation and digestibility were studied in dry cows fitted with ruminal and duodenal cannulas. Four diets based on maize silage, lucerne hay and concentrates (65/10/25 dry matter (DM)) were compared in a 4 x 4 Latin square design experiment where the diets were: control diet (C), diet RL supplied 75 g/kg DM rolled linseeds, diet EL supplied 75g/kg DM extruded linseeds, and diet LO supplied 26 g/kg DM linseed oil and 49 g/kg DM linseed meal. The diets did not differ in total organic matter (OM) and fibre digestibility, in forestomach and intestinal OM digestibility, and in duodenal N flow. Microbial N duodenal flow tended to be lower for RL versus C diet (P

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Angus steers were grazed on unsupplemented pasture (CNTRL), pasture supplemented with 0.7% BW cracked corn (FLAX-0), FLAX-0 with 0.125% and 0.250% BW of whole flaxseed (FLAX-1 and FLAX-2). Six steers were grazed per treatment for 70. days, with start and finish weights of 458 and 508. kg. At 24. h post slaughter, longissimus thoracis were harvested, and steaks assigned to treatments of postmortem aging time under vacuum (PM; 3, 14 and 56. days) with or without five days of aerobic exposure (AE). Meat antioxidant status was higher (P< 0.05) when feeding CNTRL and FLAX-1 than FLAX-0 and FLAX-2. Under AE, lipid oxidation was highest for FLAX-2 (P< 0.05), and lowest for FLAX-1. Greatest TBARs and lowest antioxidant capacity and redness values were obtained with AE and the longer PM (P< 0.05). Beef oxidative stability through AE improved by adding a low flaxseed level to supplemented corn grain, but deteriorated by adding a high flaxseed level or by extending PM. Fil: Pouzo, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina Fil: Descalzo, Adriana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; Argentina Fil: Zaritzky, Noemi Elisabet. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: Rossetti, Luciana. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; Argentina Fil: Pavan, Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Producción y Sanidad Animal; Argentina

The gut microbiota has been implicated in obesity and its progression towards metabolic disease. Dietary interventions that target the gut microbiota have been suggested to improve metabolic health. The aim of the present study was to investigate the effect of interventions withLactobacillus paracaseiF19 or flaxseed mucilage on the gut microbiota and metabolic risk markers in obesity. A total of fifty-eight obese postmenopausal women were randomised to a single-blinded, parallel-group intervention of 6-week duration, with a daily intake of eitherL. paracaseiF19 (9·4 × 1010colony-forming units), flaxseed mucilage (10 g) or placebo. Quantitative metagenomic analysis of faecal DNA was performed to identify the changes in the gut microbiota. Diet-induced changes in metabolic markers were explored using adjusted linear regression models. The intake of flaxseed mucilage over 6 weeks led to a reduction in serum C-peptide and insulin release during an oral glucose tolerance test (PPPFaecalibacteriumspecies. These changes in the microbiota could not explain the effect of flaxseed mucilage on insulin sensitivity. The intake ofL. paracaseiF19 did not modulate metabolic markers compared with placebo. In conclusion, flaxseed mucilage improves insulin sensitivity and alters the gut microbiota; however, the improvement in insulin sensitivity was not mediated by the observed changes in relative abundance of bacterial species.

JRP session : Génétique et qualité; The introduction of n‐3 essential fatty acids (FA) into the pig diet can increase the level of these fatty acids in the meat. Numerous studies have been carried out with the incorporation of the n‐3 fatty acid precursor, C18 3 n‐3 (ALA) in the pig diet. But the human diet also needs adequate levels of the long chain fatty acids such as C22 6 n‐3 (DHA). The objective of this study was to compare the effects of the ingestion of ALA (from extruded linseed) and/or of DHA (from micro‐algae) on their deposition in the meat and in processed products. Four batches of ten pigs received, between 50 and 110 kg, isolipidic diets including lipids either as oilseed rape, extruded linseed (GLE), micro‐algae (MAG) or a GLE‐MAG mixture. In all batches, the ALA or DHA content in the meat increased according to the diet. This study shows that 100 g of cooked ham can provide approximately 400 mg of ALA or 250 mg of DHA with the GLE or MAG diets respectively, or 250 mg of ALA and 100 mg of DHA with an ALA‐DHA mixed diet. The use of micro‐algae in animal feed is thus very promising to obtain a pork product with an interesting nutritional value.

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International audience; Enriching food with omega 3 is a largely explored way of improving nutritional quality of feedstuffs. Concerning fresh meat, supplementing the animal diet with natural omega 3 seems to be the best way. However, omega 3 are fragile compounds with a high susceptibility to lipid oxidation. In Reunion Island, a study called NUTRIVOL aimed to enrich poultry meat with omega 3 by providing the animals a diet enriched with flax seeds and vitamin E as antioxidant. For 3 different diets, 160 labelled yellow female chickens were raised. They were fed during 37 days with a classical diet and the last 18 days with the test diets (control without flax seeds or vitamin E enrichment, +9% flax seeds without vitamin E enrichment, and +9% fIax seeds with vitamin E enrichment). After slaughter, meat (thigh and breast) was analysed for lipid content and fatty acid composition. Lipid oxidation was evaluated by different methods after different refrigerated storage times (2 and 9 days for breast; 3 and 10 days for thigh) and after cooking under vacuum till 72°C (after 2 and 9 days of refrigerated storage for breast and after 13 days for thigh). (Résumé d'auteur)

L’introduction de graines de lin extrudées dans l’alimentation animale permet de modifier le régime de l’homme et en particulier le profil des acides gras des lipides sanguins dans le sens d’un enrichissement en acides gras n-3 et en acides gras conjugués. Ceci ouvre des perspectives intéressantes en termes de prévention pour se rapprocher des régimes de type crétois, sans changement des habitudes alimentaires.

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International audience; This experiment studied the effect of 3 different physical forms of linseed fatty acids (FA) on cow dairy performance, milk FA secretion and composition, and their relationship with methane output. Eight multiparous, lactating Holstein cows were assigned to 1 of 4 dietary treatments in a replicated 4 x 4 Latin square design: a control diet (C) based on corn silage (59%) and concentrate (35%), and the same diet supplemented with whole crude linseed (CLS), extruded linseed (ELS), or linseed oil (LSO) at the same FA level (5% of dietary dry matter). Each experimental period lasted 4 wk. Dry matter intake was not modified with CLS but was lowered with both ELS and LSO (-3.1 and -5.1 kg/d, respectively) compared with C. Milk yield and milk fat content were similar for LSO and ELS but lower than for C and CLS (19.9 vs. 22.3 kg/d and 33.8 vs. 43.2 g/kg, on average, respectively). Compared with diet C, CLS changed the concentrations of a small number of FA; the main effects were decreases in 8:0 to 16:0 and increases in 18:0 and cis-9 18:1. Compared with diet C (and CLS in most cases), LSO appreciably changed the concentrations of almost all the FA measured; the main effects were decreases in FA from 4:0 to 16:0 and increases in 18:0, trans-11 16:1, all cis and trans 18:1 (except trans-11 18:1), and nonconjugated trans 18:2 isomers. The effect of ELS was either intermediate between those of CLS and LSO or similar to LSO with a few significant exceptions: increases in 17:0 iso; 18:3n-3; trans-11 18:1; cis-9, trans-11 conjugated linoleic acid; and trans-11, trans-13 conjugated linoleic acid and a smaller increase in cis-9 18:1. The most positive correlations (r = 0.87 to 0.91) between milk FA concentrations and methane output were observed for saturated FA from 6:0 to 16:0 and for 10:1, and the most negative correlations (r = -0.86 to -0.90) were observed for trans-16+cis-14 18:1; cis-9, trans-13 18:2; trans-11 16:1; and trans-12 18:1. Thus, milk FA profile can be considered a potential indicator of in vivo methane output in ruminants.

International audience; In this study, we investigated the effect of supplementation of the maternal diet with linseed oil [rich in 18:3(n-3)) on fatty acid composition, mucosal architecture, and mast cell regulation of barrier function in piglet ileum. Sixteen sows were fed a lard LAR)- or a linseed oil (LSO)-based diet during gestation and lactation. Fatty acid composition of maternal RBC at parturition and of milk at d 14 of lactation were determined. Fatty acid composition, villous-crypt structure, and permeability to horseradish peroxidase in Ussing chambers after mast cell degranulation were determined in the ileum of piglets at d 0, 7, and 28. At d 0, 18:3(n-3) and 20:5(n-3) levels were higher, but 22:6(n-3) and 20:4(n-6) levels were lower in both maternal RBC and piglet ileum of the LSO group. Levels of 18:3(n-3) were also higher in the milk of LSO sows. Levels of 18:3(n-3) were higher in LSO piglet ileum at d 7 and 28. Moreover, at d 28, 20:4(n-6) ileal levels tended (P = 0.09) to be lower in LSO than in LAR piglets, in parallel with a lower mRNA expression of Delta 5 desaturase. LSO piglets had shorter villi at d 0 and shorter crypts at d 7 compared with LAR piglets. The effect of mast cell degranulation on ileal permeability decreased with age in both groups but reached a minimum sooner in the LSO group (d 7) than in the LAR group (d 28). In conclusion, linseed oil supplementation of the maternal diet profoundly modifies the fatty acid composition, structure, and physiology of the offspring ileum. J. Nutr. 139: 1110-1117, 2009.

International audience; This review summarizes recent developments on the utilization of specific fatty acids to modulate bovine energy metabolism, with emphasis on the periparturient dairy cow. A number of experiments have assessed the effects of polyunsaturated fatty acids on bovine hepatic energy metabolism using in vitro and in vivo models. Treatment of hepatocytes with specific fatty acids altered energy metabolism in vitro. For example, linolenic acid seemed to decrease hepatocyte triacylglycerol accumulation. This effect was confirmed in vivo, using parenteral infusions of emulsions derived from different fat sources to feed-restricted non-lactating cows. Additionally, polyunsaturated fatty acids can increase whole body response to insulin, potentially enhancing antilipolytic effects of insulin and muscle protein anabolism in the bovine. There is limited literature on the effects of feeding fat sources rich in omega-3 polyunsaturated fatty acids, such as fish oil and linseed oil, on metabolism of periparturient dairy cows. Available research has yielded conflicting results which need further clarification. On the other hand, specific isomers of conjugated linoleic acid consistently induce milk fat depression and are able to decrease energy export in milk by periparturient dairy cows. Nonetheless, research is still needed to assess whether these effects will ultimately benefit productivity and health status of periparturient dairy cows. Limitations of available methods to protect fatty acids from ruminal biohydrogenation are also addressed.

International audience; The outermost mucilaginous layer of the seed is a major, valuable component of flaxseed, but it induces arapid thickening of the medium when the seeds are immersed in water, reducing the efficiency of oil body extraction.Ultrasound can be used to extract this mucilage rapidly before the seeds are ground in water. This makes it possible toextract the oil bodies as an emulsion, with the proteins presentacting as dispersing and stabilizing agents. This emulsionis a thick fluid displaying shear-thinning and predominantly elastic behavior. This phase can be valorized directly dueto its high concentration in polyunsaturated fatty acids, high content of valuable sterols, and high arginine content of itsproteins.

Linseeds are used in ruminant feeding for a long time, but this feedstuff knows now increasing interest. Linseeds are rich in alpha-linolenic acid, a fatty acid from the omega-3 series. Despite an extensive biohydrogenation of dietary alpha-linolenic acid in the rumen, its concentration in milk and beef meat increases with linseed incorporation in diets; this increase is accompanied by that of other fatty acids produced during biohydrogenation, especially conjugated linoleic acids and trans 18:1 fatty acids. The increase in cow fertility due to omega-3 fatty acids has not been demonstrated. Furthermore, linseed incorporation in ruminant diets is one of the most efficient ways to decrease enteric methane emissions. In addition to a global mitigating effect of all lipid sources on methane, linseeds have a specific effect due to changes in rumen microbial ecosystem. The practical use of linseeds in ruminant feeding at a large scale requires the absence of negative effect at any step of the ruminant production system. An excessive supply of lipids from linseeds can have deleterious effects on digestive efficiency, milk fat and protein content, beef susceptibility to oxidation, milk and beef fatty acid composition, but when linseed incorporation in the diet does not exceed ca. 3% of additional fat, only positive effects are remaining. A challenge is the increase in linseed cropping to meet increased needs for animal feeding.

International audience; The extent and/or intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) were investigated in vitro and in situ using a raw, pre-conditioned or extruded blend of linseed and wheat bran (70:30). The duration of in vitro incubations were 2, 4, 8, 16 and 24 h, with 5 replicates. In situ studies used 3 dry ruminally fistulated Holstein cows in a 3 × 3 Latin square design, with 3 weeks adaptation to the linseed form. The diet contained 20% (DM basis) of the linseed based blend. The duration of in situ incubations were 2, 4, 8, 16, 24 and 48 h. BH was much slower in situ than in vitro, resulting in a much lower effective disappearance of C18:2 and C18:3. Moreover, the in situ technique suggested that the technological pre-treatment of linseed did not affect C18:2 and C18:3 rate of BH, whereas reduced rates were observed in vitro. After 8 h of in vitro incubation and onwards, proportions of cis-9,trans-11C18:2 were the highest with extruded linseed. The BH of FA from linseed resulted in the appearance of great proportions of trans-10+11 to trans-16C18:1 intermediates. Extrusion increased the proportions of trans-10+11C18:1 both in vitro and in situ and proportions or trans-C18:1 were higher in situ than in vitro. Compared to previous in vivo results with the same material, the in situ method provided poor estimates of BH rates and intermediates.

The extent and/or intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) were investigated in vitro and in situ using a raw, pre-conditioned or extruded blend of linseed and wheat bran (70:30). The duration of in vitro incubations were 2, 4, 8, 16 and 24 h, with 5 replicates. In situ studies used 3 dry ruminally fistulated Holstein cows in a 3 × 3 Latin square design, with 3 weeks adaptation to the linseed form. The diet contained 20% (DM basis) of the linseed based blend. The duration of in situ incubations were 2, 4, 8, 16, 24 and 48 h. BH was much slower in situ than in vitro, resulting in a much lower effective disappearance of C18:2 and C18:3. Moreover, the in situ technique suggested that the technological pre-treatment of linseed did not affect C18:2 and C18:3 rate of BH, whereas reduced rates were observed in vitro. After 8 h of in vitro incubation and onwards, proportions of cis-9,trans-11C18:2 were the highest with extruded linseed. The BH of FA from linseed resulted in the appearance of great proportions of trans-10+11 to trans-16C18:1 intermediates. Extrusion increased the proportions oftrans-10+11C18:1 both in vitro and in situ and proportions or trans-C18:1 were higher in situ than in vitro. Compared to previous in vivo results with the same material, the in situ method provided poor estimates of BH rates and intermediates. biohydrogenation / linseed / preconditioning / extrusion / in vitro / in situ

International audience; The extent and intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) from a blend of linseed and wheat bran (70:30) were investigated in the rumen fluid, rumen particle phase and duodenal flow. The blend was ground through a 3 mm screen and used raw or extruded, or was ground through a 6 mm screen and preconditioned. Three dry Holstein cows fitted with ruminal and duodenal cannulas were used in a 3 × 3 Latin square design, with 18 days adaptation. The diet contained 20% (DM basis) of the linseed based blend. Twelve samples taken over 3 days were composited for analysis of rumen fluid, rumen particle phase and duodenal flow. The BH of FA from linseed resulted in the appearance of a great number of C18:1 intermediates, among which trans-10+11 to trans-16C18:1 were the most abundant. The proportion of cis-9,trans-11C18:2 was low. Preconditioning coarsely ground linseed resulted in a lower extent of C18:2 and C18:3 BH, and lower proportions of trans-12 to trans-16C18:1 intermediates than extrusion or a lack of processing of finely ground linseed. On the contrary, extrusion did not affect the extent of BH and had no significant effect on the proportions of trans-C18:1 intermediates, but increased the proportion of cis-9,trans-11C18:2 in both rumen phases. Different digesta types resulted in different estimates of BH. The extent of BH and the proportions of trans-C18:1 intermediates were lower in the rumen particle phase and higher in the rumen fluid than in the duodenum. Moreover, interactions between digesta type and treatment of linseed were observed.

International audience; The extent and intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) from a blend of linseed and wheat bran (70:30) were investigated in the rumen fluid, rumen particle phase and duodenal flow. The blend was ground through a 3 mm screen and used raw or extruded, or was ground through a 6 mm screen and preconditioned. Three dry Holstein cows fitted with ruminal and duodenal cannulas were used in a 3 × 3 Latin square design, with 18 days adaptation. The diet contained 20% (DM basis) of the linseed based blend. Twelve samples taken over 3 days were composited for analysis of rumen fluid, rumen particle phase and duodenal flow. The BH of FA from linseed resulted in the appearance of a great number of C18:1 intermediates, among which trans-10+11 to trans-16C18:1 were the most abundant. The proportion of cis-9,trans-11C18:2 was low. Preconditioning coarsely ground linseed resulted in a lower extent of C18:2 and C18:3 BH, and lower proportions of trans-12 to trans-16C18:1 intermediates than extrusion or a lack of processing of finely ground linseed. On the contrary, extrusion did not affect the extent of BH and had no significant effect on the proportions of trans-C18:1 intermediates, but increased the proportion of cis-9,trans-11C18:2 in both rumen phases. Different digesta types resulted in different estimates of BH. The extent of BH and the proportions of trans-C18:1 intermediates were lower in the rumen particle phase and higher in the rumen fluid than in the duodenum. Moreover, interactions between digesta type and treatment of linseed were observed.

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