Effect of co-products from olive-oil production chain on rumen microbial communities: an in vitro study

Several edible agro-industrial co-products have been studied as unconventional ingredients in ruminant diets to reduce the environmental impact of food production chains. When the chemical profile of co-products is characterised by the presence of bioactive molecules, they represent a promising tool to modulate rumen microbiota activity. In the Mediterranean area, the olive oil production chain generates olive oil pomace and olive tree leaves post-milling that are animal edible bio-waste. Two in vitro trials were carried out to investigate the effect of olive oil pomace and olive tree leaves as dietary ingredients on rumen fermentation and microbiome ecology. Two experimental diets, respectively containing olive oil pomace or olive tree leaves, and the related control diets, formulated to be isoproteic and isoenergetic, were fermented and then collected after 6h and 24h. Olive oil pomace increased the content of C18:1 c9 and C18:3 c9c12c15. Considering the microbial communities, the genera Butyrivibrio, Fibrobacter, and Pseudobutyrivibrio were less abundant, while Christensenellaceae_R-7_group, Manheimia, Uruburuella were more abundant in rumen liquor fermented with olive oil pomace. Similarly, the diet containing olive tree leaves increased the content of C18:1 c9 and C18:3 c9c12c15 and decreased the abundance of Pseudobutyrivibrio and Rikenellaceae_RC9_gut_group. Data reported in this study showed that the two by-products deriving from the olive oil production chain are effective in modulating microbial community in a selective manner.