Thirty lactating dairy cows were used in a 3 3 3 Latin-square design to investigate the effects of a raw or extruded blend of linseed and wheat bran (70:30) on plasma and milk fatty-acids (FA). Linseed diets, containing 16.6% linseed blend on a dry-matter basis, decreased milk yield and protein percentage. They decreased the proportions of FA with less than 18 carbons in plasma and milk and resulted in cis-9, cis-12, cis-15 18:3 proportions that were more than three and four times higher in plasma and milk, respectively, whereas cis-9, cis-12 18:2 proportions were decreased by 10-15%. The cis-9, trans-11, cis-15 18:3 isomer of conjugated linolenic acid was not detected in the milk of control cows, but was over 0.15% of total FA in the milk fat of linseed-supplemented cows. Similarly, linseed increased plasma and milk proportions of all biohydrogenation (BH) intermediates in plasma and milk, including the main isomer of conjugated linoleic acid cis-9, trans-11 18:2, except trans-4 18:1 and cis-11, trans-15 18:2 in plasma lipids. In milk fat, compared with raw linseed, extruded linseed further reduced 6:0-16:0 even-chain FA, did not significantly affect the proportions of 18:0, cis-9 18:1 and cis-9, cis-12 18:2, tended to increase cis-9, cis-12, cis-15 18:3, and resulted in an additional increase in the proportions of most BH intermediates. It was concluded that linseed addition can improve the proportion of conjugated linoleic and linolenic acids, and that extrusion further increases the proportions of intermediates of ruminal BH in milk fat.
-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. était broyé à la grille de 3 mm et utilisé cru ou extrudé, ou broyé à la grille de 6 mm et précon-ditionné. Trois vaches Holstein taries, équipées de canules ruminale et duodénale, ont été utilisées dans un protocole en carré latin 3 × 3, avec 18 jours d'adaptation par période. La ration contenait 20 % (par rapport à la matière sèche) de mélange à base de lin. Douze échantillons de phases solide et liquide du rumen et de contenu duodénal, ont été prélevés sur 3 jours et mélangés avant analyse. La BH des acides gras du lin a conduit à l'apparition d'un grand nombre d'intermédiaires C18:1trans, parmi lesquels les trans-10+11 à trans-16 étaient les plus abondants. La proportion de C18:2cis-9,trans-11 était faible. Le préconditionnement du mélange grossièrement broyé a conduit à une BH de C18:2 et C18:3 et des proportions de C18:1trans-12 à trans-16 plus faibles que l'extrusion ou l'absence de traitement de mélange finement broyé. Au contraire, l'extrusion n'a pas modifié l'importance de la BH ou les proportions de C18:1trans, mais a augmenté la proportion de C18:2cis-9,trans-11 dans le rumen. Les différents types de prélèvement ont conduit à différentes estimations de la BH. L'importance de la BH et les proportions d'intermédiaires trans-C18:1 étaient plus faibles dans la phase solide et plus élevées dans la phase liquide du rumen que dans le contenu duodénal. En outre, des interactions entre type de digesta et traitement du lin ont été observées.b...
-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. a été beaucoup plus lente in situ qu'in vitro, si bien que la disparition effective de C18:2 et C18:3 y était beaucoup plus faible. De plus, la technique in situ a suggéré que le pré-traitement technologique n'affecte pas la vitesse de BH de C18:2 et C18:3, alors qu'une vitesse réduite a été montrée in vitro. Après 8 heures d'incubation, les proportions les plus élevées de C18:2cis-9,trans-11 étaient observées avec le lin extrudé. La BH des AG du lin a conduit à l'apparition de proportions importantes de C18:1trans-10+11 à trans-16. L'extrusion a accru les proportions de C18:1trans10+11 in vitro et in situ, et les proportions de C18:1trans étaient plus élevées in situ qu'in vitro. Par comparaison à des résultats obtenus in vivo avec les mêmes formes de lin, la méthode in situ n'a pas permis d'obtenir de bonnes estimations de la vitesse et des intermédiaires de biohydrogenation.biohydrogénation / lin / préconditionnement / extrusion / in vitro / in situ
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