Potential role of the bovine rumen microbiome in modulating milk composition and feed efficiency

Abstract

Ruminants are completely dependent on their microbiota for feed digestion and consequently, their viability. It is therefore tempting to hypothesize a connection between the composition and abundance of resident rumen bacterial taxa and the physiological parameters of the host. Using a pyrosequencing approach, we characterized the rumen bacterial community composition in 15 dairy cows and their physiological parameters. We analyzed the degree of divergence between the different animals and found that some physiological parameters, such as milk yield and composition, are highly correlated with the abundance of various bacterial members of the rumen microbiome. One apparent finding was a strong correlation between the ratio of the phyla Firmicutes to Bacteroidetes and milk-fat yield. These findings paralleled human studies showing similar trends of increased adiposity with an increase in Bacteroidetes. This correlation remained evident at the genus level, where several genera showed correlations with the animals' physiological parameters. This suggests that the bacterial community has a role in shaping host physiological parameters. A deeper understanding of this process may allow us to modulate the rumen microbiome for better agricultural yield through bacterial community design.

Figure 1. Phylum level composition.

(A) Stacked bar plot showing the phylum-level composition for each individual cow rumen sampled. (B) Ratio of Firmicutes to Bacteroidetes.

Figure 2. Correlation between milk-fat yield and Firmicutes-to-Bacteroidetes ratio.

Scatter plot showing the amount of fat produced per day for each cow (X-axis), vs. the Firmicutes-to-Bacteroidetes ratio. Each point represents one individual cow. R² of the linear regression is shown in the upper right corner of the plot.

Figure 3. Correlation between efficiency parameter and genus abundance.

Pearson linear correlation matrix of the dominant bacterial genera across the rumen samples. The genera were included in the matrix if they were in at least 50% of the cows and represented at least 0.1% of the bacterial community in at least one of the cows. Strong correlations are indicated by large squares, weak correlations by small squares. The scale colors denote whether the correlation is positive (closer to 1, blue squares) or negative (closer to −1, red squares) between the genera and the efficiency parameters. Color coding represents the phylum to which each genus belongs, as follows: Actinobacteria (green), Bacteroidetes (blue), Firmicutes (red), Proteobacteria (orange), Spirochaetes (purple), Tenericutes (light blue), TM7 (olive), Cyanobacteria (black).

Figure 4. Abundance of genera within the phylum Firmicutes compared to the genus Prevotella.

Stack bar showing the abundance of genera belonging to the phylum Firmicutes that were negatively correlated with Prevotella abundance. These included all genera that were in at least half of the cows sampled and constituted 0.1% of the reads in at least one cow. The gray portion of the bars represents the abundance of Prevotella (phylum Bacteroidetes). The dashed line separates samples with more than 50% Prevotella (left side) and from those with less than 50% Prevotella.