Impact of increasing dietary concentrations of quebracho tannins on the ruminal and fecal microbiota of dairy goats

Abstract

Abstract Condensed tannins may reduce enteric methane emissions in dairy goats by acting on feed digestibility and promoting microbial community composition shifts. We assessed the impact on the ruminal and fecal microbiota of a dietary integration with condensed quebracho tannins (CT) at three different levels (2%, Q2; 4%, Q4; 6% on dry matter, Q6) compared with a control diet (C), in a repeated 4 × 4 Latin square feeding scheme with four goats per square. The ruminal and fecal bacterial, archaeal, fungal, and protozoan microbiota were assessed at the end of each feeding period. The results were then evaluated in relation to CH4 and short chain fatty acid (SCFA) production, nitrogen excretion, and feed efficiency. In the rumen, a reduction in prokaryotic alpha-diversity was observed. Beta-diversity was also significant, with the strongest impact for the Q6 diet. Increasing CT concentrations induced more significant community shifts. The phylum Bacteroidota were enriched by all three CT levels, leading to inversion of the Bacteroidota/Firmicutes ratio. Methanobrevibacter with the corresponding phylum (Euryarcheota) and family (Methanobacteriaceae) were reduced by Q6. Ruminococcaceae, Synergistaceae and Flexilinea and Fretibacterium decreased, while Prevotellaceae, Acidaminococcaceae, Succiniclasticum and Fibrobacter increased. The diet did change the overall fungal biodiversity of the rumen, dominated by Neocallimastix, Feramyces, and Caecomyces. In the protozoal microbiota, dominated by Entodinium, only Diplodinium decreased, while Polyplastron and Isotrichia increased. In the feces, alpha and beta-diversity did not change significantly. In feces, the genus Methanobrevibacter and the corresponding phylum and family (Euryarcheota and Methanobacteriaceae, respectively) were increased by CT. The Q6 diet reduced fecal Arcanobacterium, Anaerococcus, and Megasphaera, while it enriched Alistipes and Corynebacterium. Malassezia dominated the fecal fungal microbiota with an average relative abundance of over 95%. Significant changes were observed in the feces for different fungal genera. In conclusion, increasing levels of CT in the diet induced increasingly relevant changes in the rumen microbiota of goats, including a reduction in the abundance of microbial taxa responsible for methane production. On the other hand, CT affected feed conversion efficiency, and this should be taken into account as a contributing factor in the total reduction of methane emissions.