The rumen microbiome and metabolome profile of Ongole crossbreed cattle fed probiotics and protected amino acids.

This study aimed to investigate the microbial population dynamics and metabolite profiles of Ongole crossbreed cattle (OCC) fed a combination of feed additives using metagenomic and metabolomic analyses. A crossover design was employed, involving four 3-year-old fistulated OCC bulls, each receiving four distinct dietary treatments per experimental period, followed by a washout phase with a basal diet. The treatments consisted of a basal diet (G1) as control, and the addition of feed additives as follows: G2: probiotics (Lactiplantibacillus plantarum); G3: premix; G4: G2 + G3 + amino acids lysine and methionine; and G5: G2 + G3 + amino acids protected with tannin. Rumen fluid was collected for the analysis of microbiome dynamics and metabolite profiles. The bacterial communities in diets G1, G2, G3, and G5 exhibited similar compositions, dominated by Bacteroidota, particularly the genus Prevotella. The G5 diet successfully suppressed the population of archaea, notably Methanosarcinales and Methanobacteriales, which are associated with methane production. A total of 28 significant metabolites (VIP > 1) was identified in rumen fluid, including lipid prenols, phenolic compounds, indoles and derivatives, saturated and unsaturated hydrocarbons, fatty acyls, benzene derivatives, and organooxygen compounds. The volatile compounds profile of rumen fluid showed a marked increase in prenol lipid compounds, especially in the G5 diet. Additionally, Methanosarcinales and Methanobacteriales were negatively correlated with prenol lipid levels. The inclusion of probiotics and protected amino acids alters the microbiome community structure and metabolites, positively affecting ruminant productivity.