Effects of Eucommia ulmoides Leaf Extract on Growth Performance, Serum Biochemistry, Rumen Microbiota, and Metabolic...

This study aimed to investigate the effects of adding Eucommia ulmoides leaf extract (ELE) to the diet on the growth performance, serum biochemical parameters, rumen fermentation parameters, rumen microorganisms and metabolites of yaks. Ten male yaks (two years old) were selected and randomly divided into two groups (n = 5). The control group (C, 153.48 ± 7.48 kg) was fed the basal diet, while the experimental group (H, 146.72 ± 1.87 kg) was fed the basal diet supplemented with 1.0 g/kg feed dry matter (DM) of ELE for 75 days. The results showed that the average daily gain, the serum total antioxidant capacity, catalase, and superoxide dismutase were significantly higher in the H group than in the C group (p < 0.01), while the serum total cholesterol, creatinine, alkaline phosphatase, blood urea nitrogen, and malondialdehyde were significantly lower than those of the C group (p < 0.05); in contrast, low-density lipoprotein cholesterol was significantly elevated in the H group (p < 0.01). Furthermore, the concentrations of acetate, butyrate, and hexanoic acid increased significantly compared with the C group (p < 0.05); 2-Hydroxypropanoic acid, butanedioic acid, and pentanedioic acid decreased significantly in the H group compared with the C group (p < 0.05). The metagenomic analysis revealed that ELE not only promoted the growth of cellulose-degrading bacteria but also significantly reduced the abundance of the virulence factors and carbohydrate-active enzymes (p < 0.05). In the experimental and control groups, the dominant microorganisms were Bacillota and Prevotellaceae, respectively. Metabolomics analysis further revealed that the differential metabolites were significantly enriched in pathways including purine metabolism, β-alanine metabolism, glutathione metabolism, and cGMP-PKG. The Pearson correlation analysis revealed that there were interactions among various microorganisms and metabolites, which can promote the growth and health of yaks. In conclusion, ELE can promote the growth and health of yaks by regulating the serum biochemical parameters, rumen fermentation, rumen microbial flora, and metabolism.