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

Abstract

Introduction: Microbial 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 methods: We 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 discussion: Most 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.

Keywords: biohydrogenation; dairy cow; milk fat depression; ruminal bacteria; trans-10 fatty acids.

Figure 1

Relationship between rumen trans-10/trans-11 ratio and milk fat content in the field study.

Figure. 2

Mint sparse partial least square discriminant analysis on rumen bacterial genera: variable importance in projection (left) and relevance network with a 0.6 cut-off (right).

Figure. 3

Mint sparse partial least square discriminant analysis on rumen bacterial OTUs: sample plot on the sPLS-DA components 1 and 2 (up), variable importance in projection on component 1 (bottom left) and relevance network with a 0.6 cut-off (bottom right).

Figure. 4

Scatterplots of the relationship between rumen trans-10/trans-11 ratio, trans-10 an trans-11 fatty acids percentages and GBM-transformed relative abundance of OTU52.

Figure 5

Correlation coefficients between genera or species and rumen trans-10 / trans-11 ratio in our experiment (a) and the experiment of Dewanckele et al. (2019) (b), or with trans-10 isomers percentage in the liquid (c) or solid (d) phases of the rumen in the experiment of Pitta et al. (2018), or with milk percentages of trans-10 C18:1 in the experiments of Pitta et al. (2020) (e) and Rico et al. (2015) (f). Only taxa analyzed in our study or at least two studies were selected. Color name coding represents the phylum to which each genus belongs: Actinobacteria (green), Bacteroidetes (blue), Desulfobacterota (black), Fibrobacteres (orange), Firmicutes (red), Proteobacteria (purple), Spirochaetae (pink) and Tenericutes (brown). sPLS-DA discriminant genera are underlined.

Figure 6

Receiving operator characteristic curves discriminating between trans-10/trans-11 ratio classes at genus (left) and OTU (right) levels.