Effects of preconditioning and extrusion of linseed on the ruminal biohydrogenation of fatty acids. 2. In vitro and in situ studies

Abstract

-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

Assessing rumen biohydrogenation and its manipulation in vivo, in vitro and in situ

“…The adequate identification of oleic acid in the batch in vitro incubations under consideration allowed the calculation of the net gain of 18:0 [3] which has been related to the amounts of C 18 PUFA lost. Oleic acid concentrations in 24-h incubations of Akraim et al [2] were not reported and in this case an average BH value of oleic acid (491 g/ kg) has been assumed to calculate the oleic acid remaining after 24 h. The linear relationship revealed that a constant proportion (0.666; Fig. 4) of hydrogenated C18 PUFA was transformed into the saturated end-product, 18:0 ( Fig.…”

“…This is unlikely as EFA in intact protective structures such as oleosomes probably will be predominant in the lipid residues in the bags, whereas these structures will have been destroyed in the lipids that have left the bags. This could explain both the low BH of PUFA and the low 18:0 proportions in 24-h incubated bags, when compared to in vitro [73] or in vitro and in vivo [2,49] measurements. However, it cannot explain the higher 18:1 trans proportions in the bag residues compared to in vitro or in vivo.…”

“…Alternatively, fatty acids that do not originate from the test product can be excluded by subtracting the amounts of fatty acids in blank (without the test product) incubation flasks (e.g. [2]):…”

“…To our knowledge, the effect of heat treatment, i.e. extrusion, on PUFA BH has been assessed using both in vitro and in vivo approaches for one seed only [2,49]. Comparison of other in vitro and in vivo data is limited as different technological processes and different oilseeds were used, which illustrates the need for further in vitro-in vivo comparisons of processed oilseeds.…”

“…The in sacco methodology is considered a convenient compromise between the expensive in vivo approach using duodenal cannulas and the in vitro procedures using a non-physiological environment. Traditionally, in sacco procedures were applied to assess rumen protein and fiber degradation, and only a limited number of studies used this technique to assess rumen BH [2,[71][72][73][74]. This might not be surprising as the in situ disappearance of PUFA might originate both from physical losses of (esterified) PUFA from the bag as well as from BH, which would result in an overestimation of PUFA BH.…”