Ruminal bacterial community change in response to diet-induced variation of ruminal trans-10 fatty acids

Trans fatty acids (FA) are produced during the biohydrogenation of linoleic acid in the rumen. Because of their health‐promoting properties, trans‐11 isomers, which are usually the most abundant biohydrogenation intermediates, are most desirable (1). However, in high yielding dairy cows, when high concentrate diets containing fat are fed to cows, a shift from trans‐11 to trans‐10 FA can occur, therefore, trans‐10 isomers can become the predominant biohydrogenation intermediates, inducing milk fat depression in dairy cows(2) and having possible detrimental effects on human health(3). The aim of this work was to study the bacterial community dynamics in response to diet‐induced trans‐10 FA shift

Effect of cow diet on the ruminal microflora and its in vitro fatty acid production

The objective of this study was to investigate the effects of donor’s cow diet (hay or maize silage plus concentrates) on ruminal bacteria count, flora diversity and fatty acids profile (FA) of ruminal fluid and in vitro biohydrogenation (BH) of C18:2. Two dry cows fitted with a ruminal canula were used in a 2x2 design. Each period included three weeks of diet adaptation and two weeks of sampling. The cows were fed twice daily either a diet (H) composed of grass (38%) and alfalfa hay (62%) or an acidogenic diet (A) composed of maize silage (38%), wheat (57%) and soybean (5%) meal. Ruminal fluid was sampled and centrifugated (150g, 5min., 39°C). The ruminal fluid (80mL) was mixed with 80mL of buffer, a fermentative substrate and grape seed oil as source of C18:2 before being incubated during 6 hours at 39°C in anaerobic and dark conditions. Biodiversity was estimated by the Simpson index modified by Haegeman et al.1 after SSCP analysis, and FA were analysed by GLC. Bacteria counting was realised according to Oblinger and Koburger2 (1975). Total and cellulolytic bacteria contents were higher in inoculum A than in inoculum H (9.3.109 vs. 2.4.108/mL for total bacteria and 2.4.108 vs. 1.6.107/mL for cellulolytic bacteria). No difference in the biodiversity of the inoculums was noticed according to the cow or the diet, but diversity during period 1 tended to differ (P=0.09) from period 2, suggesting a time variation of flora biodiversity. Before incubation, the ruminal fluid from the cow receiving diet A contained significantly (P<0.01) more C18:2, trans-10 and trans-11 C18:1, and odd-chain FA than inoculum from the cow receiving diet H. After incubation, inoculum A resulted in a significantly (P<0.01) greater BH of C18:2 than inoculum H, and produced more trans-10C18:1, trans-11C18:1 and odd-chain FA (P<0.01) Trans-10 and odd-chain FA are known to be increased by a high concentrate diet, which explains that inoculum A was richer in these FA than inoculum H. The ruminal flora selected in vivo by diet A continued the production of these FA in vitro. The greater content of trans-11C18:1 and of C18:2 in the inoculum A could be explained by the greater content in C18:2 of the diet A. During incubation with added C18:2, inoculum A continued to produce more trans-11 along with a higher C18:2 BH than inoculum H, which could be due to the higher concentration of cellulolytic bacteria in the inoculum A

Temperature and duration of heating of sunflower oil affect ruminal biohydrogenation of linoleic acid in vitro

Sunflower oil heated at 110 or 150°C for 1, 3, or 6 h was incubated with ruminal content in order to investigate the effects of temperature and duration of heating of oil on the ruminal biohydrogenation of linoleic acid in vitro. When increased, these 2 parameters acted together to decrease the disappearance of linoleic acid in the media by inhibiting the isomerization of linoleic acid, which led to a decrease in conjugated linoleic acids and trans-C18:1 production. Nevertheless, trans-10 isomer production increased with heating temperature, suggesting an activation of Δ9-isomerization, whereas trans-11 isomer production decreased, traducing an inhibition of Δ12-isomerization. The amount of peroxides generated during heating was correlated with the proportions of biohydrogenation intermediates so that they might explain, at least in part, the observed effects. The effects of heating temperature and duration on ruminal bacteria community was assessed using capillary electrophoresis single-strand conformation polymorphism. Ruminal bacterial population significantly differed according to heating temperature, but was not affected by heating duration. Heating of fat affected ruminal biohydrogenation, at least in part because of oxidative products generated during heating, by altering enzymatic reactions and bacterial population

Random changes in the heifer rumen in bacterial community structure,physico-chemical and fermentation parameters, and in vitro fiber degradation

The variability over time of several main ruminal characteristics was studied in heifers over 15 consecutive weeks. Three heifers were assigned to a low-fiber diet (27% NDF) and three to a high-fiber diet (44% NDF). The physico-chemical (pH and redox potential) and fermentation(volatile fatty acids and ammonia contents) parameters were determined on 1 day per week for 15 consecutive weeks. On the same days the bacterial community structure was studied using a molecular fingerprint technique and the ruminal fiber degradation was studied by in vitro incubation of a withdrawn ruminal content sample. Numerous random changes were observed from week to week for all physico-chemical and fermentative parameters and in vitro fiber degradation. The redox potential was the only parameter to show a significant interaction between diet and week. Except for the ammonia content, the amplitudes of fluctuations observed were higher for the low-fiber diet. The bacterial community structure did not differ between diets or weeks. The in vitro fiber degradation was similar for both diets, with numerous random changes throughout the study. The findings of this study indicated that most of the parameters of the ruminal ecosystem had time-related changes with random fluctuations around a mean value which reflect an unstable equilibrium. This conclusion was valid for both low- and high-fiber diets

Etude par pyroséquençage haut débit (454) de l’implantation des bactéries au niveau du rumen du veau laitier, de sa naissance au sevrage

Objectif : Décrire la séquence temporelle d'implantation de la population bactérienne au niveau du rumen chez le veau, de la naissance jusqu'au sevrage, via des outils de microbiologie moléculaire

The ruminal level of trans-10 fatty acids of dairy cows is linked to the composition of bacterial community

The ruminal level of trans-10 fatty acids of dairy cows is linked to the composition of bacterial communit

From high throughput 454 GS FLX data analysis process of 16S RNA gene sequences using barcoding to bacterial community exploration

From high throughput 454 GS FLX data analysis process of 16S RNA gene sequences using barcoding to bacterial community exploratio

Mesure in vitro de l'activité de la communauté bactérienne ruminale

Les techniques modernes de biologie moléculaire permettent une description de la micropopulation ruminale. L’étude de l’activité de cette population sur les principaux constituants de la ration est souvent réalisée in vitro. L’objectif de cette étude était de vérifier si la population bactérienne est active mais n’évolue pas pendant une courte incubation in vitro, ce qui permettrait de mettre en relation le profil et l’activité des bactéries. La communauté bactérienne mise à incuber in vitro n’a pas évolué, ni en quantité, ni en structure ou en diversité, ce qui suggère que les conditions de culture n’entraînent pas une sélection de certaines espèces au cours des 6 premières heures. Cette communauté est restée active, puisque capable de dégrader les différents substrats : matières azotées, glucides et lipides. Une mesure in vitro de l’activité microbienne est donc possible, et pourrait s’avérer intéressante à associer aux techniques de biologie moléculaire afin de mieux caractériser la communauté bactérienne d’un prélèvement

Integrating data from spontaneous and induced trans-10 shift of ruminal biohydrogenation reveals discriminant bacterial community changes at the OTU level

IntroductionMicrobial digestion is of key importance for ruminants, and disturbances can affect efficiency and quality of products for human consumers. Ruminal biohydrogenation of dietary unsaturated fatty acids leads to a wide variety of specific fatty acids. Some dietary conditions can affect the pathways of this transformation, leading to trans-10 fatty acids rather than the more usual trans-11 fatty acids, this change resulting in milk fat depression in dairy cows.Materials and methodsWe combined data from an induced and spontaneous trans-10 shift of ruminal biohydrogenation, providing new insight on bacterial changes at different taxonomic levels. A trans-10 shift was induced using dietary addition of concentrate and/or unsaturated fat, and the spontaneous milk fat depression was observed in a commercial dairy herd.Results and discussionMost changes of microbial community related to bacteria that are not known to be involved in the biohydrogenation process, suggesting that the trans-10 shift may represent the biochemical marker of a wide change of bacterial community. At OTU level, sparse discriminant analysis revealed strong associations between this change of biohydrogenation pathway and some taxa, especially three taxa belonging to [Eubacterium] coprostanoligenes group, Muribaculaceae and Lachnospiraceae NK3A20 group, that could both be microbial markers of this disturbance and candidates for studies relative to their ability to produce trans-10 fatty acids