The Dairy Cattle Fecal Microbiota Response to Diet Supplementation with Plant Secondary Metabolites

Twenty-four early to mid-lactation dairy cows were randomized to either a top dress treatment (a blend of quebracho and chestnut extracts along with a carrier from cereals rich in saponins) or un-supplemented control ration (CON) for a 64-day trial. Animals were blocked on parity, dry matter intake, baseline CH4, and days in milk. Animals were group-housed and individually fed twice per day. Fresh feces were collected from each cow at baseline (Day 0), and at days 16, 32, and 64. Using 16S rRNA gene amplicon sequencing, a total of 1,538 amplicon sequence variants were identified after filtering. While feed additives like that tested here, have been implemented successfully (to reduce CH4 emissions and reactive N in excreta), our results suggest that the microbiota can tolerate low doses of a tannin-based product, leading to no long-term changes. Higher doses may be more efficacious, but cost prohibitive.