Gut microbiota are closely linked to host health and adaptability to different geographical environments. However, information on the influence of different geographical conditions on the intestinal microbiota of yaks is limited. In this study, 18 yak fecal samples were collected from three regions of China, namely Shangri-la, Lhasa, and Yushu, and were analyzed via high-throughput sequencing. The alpha diversity, as measured by the Shannon, ACE, and Chao indices, was the highest in the Shangri-la samples. Principal coordinate analysis detected significant differences in the composition of the intestinal microbiota of yaks from different regions. A total of six phyla, 21 families, and 29 genera were identified in the fecal samples. The dominant phyla in the samples were Firmicutes and Bacteroidetes, and the most abundant family was Ruminococcaceae. In addition, Ruminococcaceae_UCG-005 was the predominant genus and was more abundant in Yushu samples than in other samples. However, the predicted functional gene composition of the gut microbiota of yaks from different regions was similar. Our results revealed that geographical conditions influence the diversity and composition of the intestinal microbiota of yaks.
Current information on the differences between rumen bacteria and metabolites of the grass-fed and grain-fed yaks is limited. Understanding the composition and alterations of rumen microbial metabolites is important to clarify its potential role in grass-fed and grain-fed systems. The aim of this research was to explore the influence of different production systems on the functional attributes and metabolites in the rumen microbiota of yak using genomics (Illumina MiSeq sequencing of the 16S rRNA gene) and untargeted metabolomics (UHPLC-QTOF-MS). Rumen samples were obtained from grass-fed (C), grain-fed for 3-month (G3), and grain-fed for 6-month yaks (G6). Results showed that the grain-fed yaks presented a lower rumen bacterial richness and diversity when compared to grass-fed yaks. Bacteroidota, Firmicutes, and Fibrobacterota were the main bacterial phyla. At the phylum and genus level, the grass-fed yaks significantly increased the abundance of Fibrobacterota and Fibrobacter (p < 0.05), respectively. The metabolomics analysis revealed that the metabolite profiles differed among the three groups. Compared with the grass-fed group, grain feeding significantly increased azelaic acid, hypoxanthine, uridine, L-phenylalanine, anserine, and decreased alpha-linolenic acid, adenine. Pathway enrichment analysis showed significant differences in metabolic pathways among all comparison groups, but the glycerophospholipid metabolism and alpha-linolenic acid metabolism pathway were common key metabolic pathways. This study showed that the combined analysis of microbiota and metabolites could distinguish different production systems and the fattening time of yaks, providing novel insights for us to understand the function of the rumen bacteria.
The thermal stability and degradation kinetics of patulin (PAT, 10 μmol/L) in pH 3.5 of phosphoric-citric acid buffer solutions in the absence and presence of cysteine (CYS, 30 μmol/L) were investigated at temperatures ranging from 90 to 150 °C. The zero-, first-, and second-order models and the Weibull model were used to fit the degradation process of patulin. Both the first-order kinetic model and Weibull model better described the degradation of patulin in the presence of cysteine while it was complexed to simulate them in the absence of cysteine with various models at different temperatures based on the correlation coefficients (R2 > 0.90). At the same reaction time, cysteine and temperature significantly affected the degradation efficiency of patulin in highly acidic conditions (p < 0.01). The rate constants (kT) for patulin degradation with cysteine (0.0036–0.3200 μg/L·min) were far more than those of treatments without cysteine (0.0012–0.1614 μg/L·min), and the activation energy (Ea = 43.89 kJ/mol) was far less than that of treatment without cysteine (61.74 kJ/mol). Increasing temperature could obviously improve the degradation efficiency of patulin, regardless of the presence of cysteine. Thus, both cysteine and high temperature decreased the stability of patulin in highly acidic conditions and improved its degradation efficiency, which could be applied to guide the detoxification of patulin by cysteine in the juice processing industry.
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