Silvafeed® Tannins Role in Rumen Microbiota Modulation

For many years dietary protein binding has been considered the main property of tannins within animal nutrition, but more recent speculations have highlighted many other mechanisms of action for tannins.

Antispasmodic effect on gastrointestinal passage, reduction of rumen starch degradation, local immune response modulation and antioxidant effect are some known examples, but perhaps the most important mechanism that explains the role of tannins, their strong and lasting impact on ruminants health and productivity, is the modulation of gastrointestinal microbiota.

This is the reason behind the study carried out by Silvateam animal nutrition experts to assess the impact of dietary tannins on rumen microbiota and its interplay with rumen physiological parameters.

The trial involved ruminally fistulated Holstein cows of the Holando−Argentino breed. After a 14 days adaptation period (both high and low starch feed intake), the animals were kept on high starch diet for 21 days, in order to ensure complete adaptation of rumen microbiota and physiological parameters before starting the actual dietary treatment. On day 36, pretreatment ruminal samples were taken from each animal before feeding (T1) and the same high starch diet was supplemented with a blend of chestnut and quebracho Silvafeed® tannins for the following 12 days, until the end of the experimental period (from day 36 to day 48). The average feed intake was 13 kg of dry matter per animal per day. Four serial ruminal samples were taken at 3, 5, 9 and 12 days after initiation of tannins supplementation (T2, T3, T4 and T5).

At each temporal step, ruminal content was collected from the ventral sac of the cows. 16S RNA of rumen stomach microbiota was purified and sequenced through high-throughput sequencing protocol. Thanks to this innovative genomic sequencing technique, Silvateam nutritionists managed to have a wide range of information regarding the rumen microbiome of the treated bovines, enabling them to assess its response to the inclusion of different tannins between T1 and T5.

The bioinformatics analysis carried out on the extracted RNA lead to some interesting results. Throughout the 12 days trial, the bacterial populations within rumen microbiome tended to homogenise and dysbiotic microbiota profiles were normalised. Firmicutes to Bacteroidetes ratio, a parameter linked to energy harvesting function in mammals, gradually increased after tannin addition, mainly by favouring members of family Ruminococcaceae to the detriment of genus Prevotella. Silvafeed® tannins had a modulation effect also on other fibrolytic, amylolytic and ureolytic bacteria. Methanogenic archaea (Metanobrevibacter and Metanosphera) suffered inhibition, thus resulting in a significant energy saving for the animal, in addition to the environmental implications of reducing the emission of greenhouse gases.

Concomitantly, ruminal pH was significantly increased and remained stable until the end of the experiment.

Another very important metabolic effect is the reduction of urease activity within ruminal liquor. Due to their antibacterial action against urease enzyme producing bacteria, tannins foster the reduction of ammonium increase rate in rumen, thus preventing degradation of urea in Rumen,. This metabolic effect, mediated by the action of tannins on bacteria with urease action, has impacts on the efficiency of both proteins and energy consumption, because less energy is needed to dotoxify ammonia in the liver.

The study results suggest a link between microbiota normalization and ruminal physiology stabilization. Silvafeed® tannins have a positive effect on these parameters, since they modulate ruminal physiology by reshaping bacterial communities, avoiding to disrupt rumen microbiota and stabilizing ruminal pH and urea degradation.