In vitro rumen fermentation traits of Mentha piperita and Rose

From the point of view of the circular economy, the organic waste, obtained after the extraction of the essential oil, could constitute an important recovery material due to their content of bioactive compounds and used as a supplement in the diet of dairy cows. The aim of this study was to evaluate the in vitro rumen fermentable characteristics of Mentha piperita and Rose, used as the residual product obtained from a supercritical CO2 extraction (Mint), and as the residual of normal extraction with glycol (Rose). Each fermentation was tested in three repeated incubations, and each incubation was carried on by using rumen fluids collected from three different dairy cows. A bottle containing only the medium, one containing only the rumen fluid, one containing grass hay supplementation, and one containing grass hay plus glycol were used as controls. Each bottle was fermented for 24 hours. Following this analysis, microbial DNA from rumen samples was extracted with a commercial kit and sequenced by Illumina NGS methodology. The different supplementations have led to the creation of different microbiota in each sample. It was possible to observe how the microbiota varied according to the method used for the essential oil extraction. In particular, all the samples collected from the bottles containing glycol (the fermentation from Rose conventional extraction and related CTRLs fermentations added with glycole) Anaerovibrio taxa was always present with significantly higher abundances (about 40 %). Anaerovibrio are known to be involved in the first step of ruminal lipid metabolism: the hydrolysis of esterified fatty acids to the free (non esterified) form and glycerol with little accumulation of mono- or diacylglycerols. The glycerol produced in this step is usually rapidly fermented from other ruminal bacteria to produce propionate. In progress are the fatty acids analysis to confirm this microbial processes.