Effects of the grass in different phenological periods on rumen fermentation and gastrointestinal tract bacteria community in grazing yak on the Qinghai-Tibetan Plateau

Abstract

Background: In this study, we investigated the effects of grass in different phenological periods on ruminal fermentation, serum biochemical indices, and gastrointestinal tract microbes in grazing yak on the Qinghai-Tibetan Plateau. A total of eighteen female freely grazing yaks with an average age of 3 years old and a body weight of 130 ± 19 kg were selected. According to the plant phenology periods, yaks were randomly allocated to one of three treatments: (1) regreen periods group (RP, n = 6); (2) grassy periods group (GP, n = 6); (3) hay periods group (HP, n = 6). At the end of the experiment, the blood, rumen fluids, and rectal contents were collected to perform further analysis. Results: Yak in the GP group increased the concentration of total volatile fatty acid (TVFA), acetate, urea acid (UA), glucose (GLU), triglyceride (TG), cholesterol (CHO), high density lipoprotein (HDL), low density lipoprotein (LDL), the abundance of Prevotella in the rumen, and the abundances of Rikenellaceae_RC9_gut_group, Eubacterium_coprostanoligenes_group, and Prevotellaceae_UCG-004 in the gut (P < 0.05). However, yak in the HP group increased the concentrations of isobutyrate, isovalerate, valerate, creatinine (CREA), the abundance of Eubacterium_coprostanoligenes_group in the rumen, and the abundances of Romboutsia and Arthrobacterin the gut (P < 0.05). Conclusions: Based on the results of rumen fermentation, serum biochemical, differential biomarkers, and function prediction, yak increased the digestion of carbohydrates via gastrointestinal tract microbes with the grass regreen and grassy. However, the gastrointestinal tract of yaks increased the risk of microbe disorders and host inflammation with the grass wither.