Effect of Dietary Protein Levels on Dynamic Changes and Interactions of Ruminal Microbiota and Metabolites in Yaks on the Qinghai-Tibetan Plateau

Abstract

To improve performance and optimize rumen function in yaks (Bos grunniens), further knowledge on the appropriate dietary protein levels for ruminal microbiota and the metabolite profiles of yaks in feedlot feeding is necessary. Current understanding of dietary protein requirements, ruminal microbiota, and metabolites is limited. In this study, yaks were fed a low-protein diet (L; 9.64%), middle low-protein diet (ML; 11.25%), middle high-protein diet (MH; 12.48%), or a high-protein diet (H; 13.87%), and the effects of those diets on changes and interactions in ruminal microbiota and metabolites were investigated. Twenty-four female yaks were selected, and the effects on ruminal microbiota and metabolites were investigated using 16s rRNA gene sequencing and gas chromatography time-of-flight/mass spectrometry (GC-TOF/MS). Diets containing different protein levels changed the composition of the rumen bacterial community, the H group significantly reduced the diversity of ruminal microbiota (p < 0.05), and the number of shared amplicon sequence variants (ASVs) between the H group and the other three groups was lower, suggesting that the ruminal microbiota community fluctuated more with a high-protein diet. In rumen, Bacteroidetes, Firmicutes, and Proteobacteria were the most abundant bacteria at the phylum level, and Bacteroidetes was significantly less abundant in the MH group than in the L and ML groups (p < 0.05). Prevotella_1, Rikenellaceae_RC9_gut_group, and Christensenellaceae_R-7_group had the highest abundance at the genus level. Prevotellaceae was enriched in the low-protein groups, whereas Bacteroidales_BS11_gut_group was enriched in the high-protein groups. Rumen metabolite concentrations and metabolic patterns were altered by dietary protein levels: organic acid metabolites, antioxidant-related metabolites, and some plant-derived metabolites showed variation between the groups. Enrichment analysis revealed that significant changes were concentrated in six pathways, including the citrate cycle (TCA cycle), glyoxylate and dicarboxylate metabolism, and butanoate metabolism. Network analysis showed promotion or restraint relationships between different rumen microbiota and metabolites. Overall, the rumen function was higher in the MH group. This study provides a reference for appropriate dietary protein levels and improves understanding of rumen microbes and metabolites.

The Response of Ruminal Microbiota and Metabolites to Different Dietary Protein Levels in Tibetan Sheep on the Qinghai-Tibetan Plateau

“…Additionally, an association was found between the structure of the rumen microbiota and metabolic profiles. These results were consistent with those in donkeys ( 64 ), yaks ( 65 ), Holstein heifers ( 18 ), mice ( 66 ) and humans ( 67 ), revealing a close relationship between microbiota, metabolites and organismal health. Our study also found significant positive correlations between the dominant bacterial groups and differential metabolites using Spearman correlation analysis.…”

Effects of Dietary Protein Levels on Sheep Gut Metabolite Profiles during the Lactating Stage

“…In our study, trend lines between the groups revealed that organic acids and their associated metabolites are the most significantly affected metabolites detected in the fecal samples. Our results are in line with the previous study [ 23 ] as they also documented organic acids’ most altering metabolites in the rumen samples of the yaks fed different dietary protein levels. The possible reason might be more protein availability for degradation, which results in greater amino-acid availability in the small intestine for microbial downstream to supply the end products for liver metabolism.…”

Effect of dietary supplementation of Ganoderma lucidum residue on growth performance, immune organ index and faecal microbial community diversity in broiler chickens

“…(4) Rikenellaceae_RC9_gut_group also belongs to the same phylum, and its members are producers of shortchain fatty acids. The higher abundance of the Rikenellaceae_RC9_gut_group ensures a high proportion of propionic acid in the rumen and thus regulates the balance in the intestine [32]. (5) norank_f__norank_o__Clostridia_UCG-014 is tolerant to gastric acid, enters the intestine, inhibits the growth of harmful intestinal bacteria, restores the function of intestinal ora, improves immunity and promotes the absorption, digestion and assimilation of nutrients [33].…”