Rumen ecology detailed study using quebracho tannin as fermentation stressing factor

The understanding of gastrointestinal physiology helps to develop feeding strategies aimed at improving the sustainability and quality of the animal production chain. Tannins are secondary plant metabolites characterized by antimicrobial properties and they can be added to the diet as rumen fermentation modulators. The rumen microbial community is predominantly affected by diet. The aim of this in vitro trial was to study the relationship among microbiota, fatty acids, and dimethyl acetals profile that are efficient biomarkers of rumen ecology. Two doses of quebracho tannin (55mg/100g on DM and 166mg/100g on DM) were added to the feed formulated for dairy ewes. The feeds were fermented with ovine rumen liquor for 24 hours. Data highlighted the effect of tannin on the rumen biohydrogenation process of C18-carbon chain: C18:1c9, C18:2n6, and C18:3n3 increased while C18:0, C18:1t9, C18:1t11, C18:1t12, C18:1c11 decreased when 166mg/100g on DM of tannin was added to the feed. Similarly, the dimethyl acetals profile was affected by the presence of the highest level of quebracho tannin: DMA-C14:0 increased and DMA-C13:0, DMA-iC14:0, and DMA-iC15:0 concentration decreased. The microbial community ratio was changed by tannin feed inclusion, and at the genus level, more bacteria abundances varied. Among genera more representative (abundance >1%), Actinobacillus (P=0.0013), Butyrivibrio (P=0.0058), Escherichia_Shigella (P<0.0001), Lachnospira (P<0.0001), Manheimia (P<0.0001), Neisseria (P<0.0001), Pseudobutyrivibrio (P<0.0001), and Succinivibrio (0.0003) increased with 166mg/100g on DM of tannin inclusion. Whilst Comamonas (P<0.0001), Faecalibacter (P=0.0008), Fusobacterium (P<0.0001), and Prevotella (P=0.0092) decreased. The results of this study confirm that fatty acids, and dimethyl acetals could be an efficient tool to understand rumen ecology.