Key mechanisms of action of a blend of plant extracts within the ruminants microbial systems.
The results of several trials and published researches coming from every part of the world have recently brought to light new modes of action that explain the reasons why tannins foster an improvement in both animal welfare and performance, going deeper than the traditionally recognised ruminal protein by-pass mode of action. These mechanisms, which are linked to various aspects of ruminants metabolism, immune system and bacterial population, are all interacting in the typically complex systems of any cattle species.
The widespread opinion coming from both research and commercial experience highlights these multiple factors as the reasons behind the beneficial effects of natural extracts. Among these factors, the mechanism which probably is the most impacting and interesting is the bacterial selection triggered by tannins within ruminal microbiota.
A recent study focused on this topic (Diaz Carrasco et al., published on BioMed Research International, 2017), assessed a group of fistulated holsteins steers by performing a high-throughput sequencing of 16S rRNA gene in order to analise the effect of supplementing a diet with Silvafeed® ByPro on the rumen microbiota bacterial population. Silvafeed® ByPro is a blend of plant extracts rich in bioactive substances designed for ruminants nutrition.
The results of this trial showed that the ratio of the phyla Firmicutes and Bacteroidetes, a parameter associated with energy harvesting function, was increased after adding Silvafeed® ByPro to the animals feed. This shift was essentially due to the selective increase of Ruminococcaceae in comparison to the members of genus Prevotella (Figure 2).
Silvafeed® ByPro altered some important bacterial communities within the rumen, including fibrolytic, amylolytic, and ureolytic bacteria, reducing the ones belonging to methanogenic archaea (Figure 3). Within the Euryarchaeota phylum, a significant reduction was observed in the ruminal concentration of the genus Methanobrevibacter and Methanosphera.
Hydrogen is known as the primary substrate for methanogens to produce methane (CH4) in the rumen. The dietary inclusion of Silvafeed® ByPro favours certain ruminal bacteria that do not lead to the metabolic production of hydrogen. As such, Silvafeed® ByPro can indirectly reduce the available hydrogen pool in the rumen and thus mitigate CH4 emissions, which is an important greenhouse gas and represents 2-12% of feed energy loss.
Other interesting results of this trial consist in the reduction of both ruminal protein degradation rate and of lactic acid producing bacteria, favouring an increase in the pH level within the rumen (Figure 4). These effects highlight Silvafeed® ByPro as a solution to be added to the ruminants diets in order to prevent any occurrence of ruminal acidosis.
In conclusion, the results of supplementing ruminants diets with Silvafeed® ByPro have shown to modulate the microbiota through a selective process, affecting different bacteria communities and increasing the Firmicutes to Bacteroidetes ratio. The interactions between all these direct and indirect mechanisms and their synergic actions are key prerequisites to favour the reduction of methane emissions, rumen metabolic acidosis and several diseases which can harm both the environment and the animal welfare, as well as the improvement in animal performance.