Impact of increasing dietary concentrations of quebracho tannins on the ruminal and fecal microbiota of dairy goats
The gut microbiota of mammals is a complex ecosystem that co-evolved with its host resulting in what is now defined as the superorganism or holobiont. Ruminants are the most representative example of this inter-dependence; being foregut fermenters, these animals rely critically on their microbiota to extract energy from otherwise indigestible substrates. Thanks to this finely evolved symbiosis, ruminants can exploit vegetable polysaccharides as nutritional sources through the anaerobic fermentation of feed material carried out by several different microbial species which leads to the formation of volatile fatty acids, hydrogen gas, and carbon dioxide. Methanogenic archaea are involved in the last step, allowing other microbial species to continue fermentations, using hydrogen and carbon dioxide to produce methane, thus reducing the partial pressure of hydrogen. Like all human activities, however, ruminant farming involves a cost for the environment. Enteric methane accounts for 3.3% of global anthropogenic greenhouse gas emissions. The release of methane results in a loss of dietary energy and a better understanding of the dietary factors influencing composition and dynamics of the rumen microbiota may facilitate the development of nutritional strategies able to reduce the production of methane by farmed ruminants and improve feed conversion efficiency.A proposed mitigation strategy is dietary supplementation with tannins. By acting as modulators of the rumen ecosystem and animal physiology, tannins can improve production and reproductive performance, animal health, efficiency of nitrogen utilization, quality of derived livestock products and reduction of the risk of meteorism, gastrointestinal parasite load and environmental impact in terms of both methanogenesis and nitrogen excretion. In this project, we assessed the impact of dietary integration with commercial purified condensed quebracho tannin (CT) extract on the goat ruminal and fecal microbiota at three different levels (2%, Q2; 4%, Q4; 6%, Q6) compared with a control diet (C), in a two-times repeated 4 x 4 Latin square feeding design with four goats per group. At the end of each feeding period of 28 days, rumen fluid and fecal swabs were collected and subjected to a microbiota characterization pipeline including bacteria, archaea, fungi, and protozoa.