Prediction of Metabolizable Energy Concentrations of Herbage in the Qinghai-Tibetan Plateau Using Tibetan Sheep Digestibility Data

Coevolution of Rumen Epithelial circRNAs with Their Microbiota and Metabolites in Response to Cold-Season Nutritional Stress in Tibetan Sheep

This study explores the effects of the coevolution of the host genome (the first genome) and gut microbiome (the second genome) on nutrition stress in Tibetan sheep during the cold season. The rumen epithelial tissue of six Tibetan sheep (Oula-type) was collected as experimental samples during the cold and warm seasons and the study lasted for half a year. The cDNA library was constructed and subjected to high-throughput sequencing. The circRNAs with significant differential expression were identified through bioinformatics analysis and functional prediction, and verified by real-time quantitative PCR (qRT-PCR). The results showed that a total of 56 differentially expressed (DE) circRNAs of rumen epithelial tissue were identified using RNA-seq technology, among which 29 were significantly upregulated in the cold season. The circRNA-miRNA regulatory network showed that DE circRNAs promoted the adaptation of Tibetan sheep in the cold season by targeting miR-150 and oar-miR-370-3p. The results of correlation analysis among circRNAs, microbiota, and metabolites showed that the circRNA NC_040275.1:28680890|28683112 had a very significant positive correlation with acetate, propionate, butyrate, and total volatile fatty acid (VFA) (p < 0.01), and had a significant positive correlation with Ruminococcus-1 (p < 0.05). In addition, circRNA NC_040256.1:78451819|78454934 and metabolites were enriched in the same KEGG pathway biosynthesis of amino acids (ko01230). In conclusion, the host genome and rumen microbiome of Tibetan sheep co-encoded a certain glycoside hydrolase (β-glucosidase) and coevolved efficient VFA transport functions and amino acid anabolic processes; thus, helping Tibetan sheep adapt to nutrient stress in the cold season in high-altitude areas.

Effects of LAB Inoculants on the Fermentation Quality, Chemical Composition, and Bacterial Community of Oat Silage on the Qinghai-Tibetan Plateau

Lactic acid bacteria (LAB) have been proposed for the control of undesirable fermentation and, subsequently, aerobic deterioration due to their ability to produce antimicrobial metabolites in silage mass. To investigate the effect of specific LAB on the silage fermentation characteristics and bacterial community composition of oat in cold regions, silages were treated without (control) or with three LAB strains (LB, Lentilactobacillus buchneri; nLP, low temperature tolerant Lactiplantibacillus plantarum; pLP, phenyllactic acid-producing Lactiplantibacillus plantarum), and then stored at ambient temperature (−2.63 ± 5.47−14.29 ± 5.48 °C) for 30, 60, and 90 days. Compared with control, inoculation of LAB decreased the final pH value, butyric acid content, ammonia-N of total N and dry matter loss of silage. Treatments with nLP and pLP increased (p < 0.05) lactic acid content, whereas LB increased (p < 0.05) acetic acid content of silage. Lactiplantibacillus and Leuconostoc dominated in the silages with relative abundance of 68.29−96.63%. A prolonged storage period enhanced the growth of Leuconostoc in pLP-treated silage. In addition, pLP increased (p < 0.05) the aerobic stability of silage as compared with nLP. In conclusion, inoculation of LAB improved silage fermentation and/or delayed aerobic deterioration by shifting bacterial community composition during ensiling. Phenyllactic acid-producing Lactiplantibacillusplantarum as an inoculant exhibited potential for high quality silage production.

Effect of phenyllactic acid on silage fermentation and bacterial community of reed canary grass on the Qinghai Tibetan Plateau

Background

This study aimed to investigate the effect of phenyllactic acid as an additive on silage fermentation and bacterial community of reed canary grass (RCG, Phalaris arundinacea L.) on the Qinghai Tibetan Plateau. At the heading stage, RCG was harvested, chopped and ensiled in small bag silos. The silage was treated without (control, 1.0 g/mL sterile water, on a fresh matter basis (FM)) or with phenyllactic acid (PLA, 3 mg/mL, FM), antimicrobial additive (PSB, a mixture of potassium sorbate and sodium benzoate, 2%, FM), lactic acid bacteria inoculant (LABi, L. plantarum + L. curvatus, 1 × 10⁶ cfu/g, FM) and PLA + LABi, and then stored in a dark room at the ambient temperature (5 ~ 15 °C) for 60 days.

Results

Compared with control, PLA decreased lactic acid, acetic acid and ammonia-N contents, and subsequently increased CP content of RCG silage. PLA enhanced the growth of lactic acid bacteria and reduced the count of yeasts (P < 0.05) in RCG silage, with reduced bacterial richness index (Chao1), observed operational taxonomic units and diversity index (Simpson). In relative to control, moreover, PLA and PLA + LABi increased the relative abundance of Lactococcus in RCG silage by 27.73 and 16.93%, respectively.

Conclusions

Therefore, phenyllactic acid at ensiling improved nutritional quality of RCG silage by advancing the disappearance of yeasts and the dominance of Lactococcus.

Rumen Fermentation-Microbiota-Host Gene Expression Interactions to Reveal the Adaptability of Tibetan Sheep in Different Periods

Simple Summary

The Qinghai-Tibet Plateau has a unique ecological environment, involving high altitude, low oxygen levels, strong ultraviolet rays, and severe imbalances in seasonal forage supply, which poses a serious threat to the livestock that feeds on natural pastures to maintain their survival. We have carried out a long-term follow-up study on rumen fermentation characteristics, the microbiota, and rumen epithelial gene expression of local Tibetan sheep. Correlation analysis showed that there were interactions among rumen fermentation characteristics, the microbiota, and host gene expression, mainly by adjusting the amino acid metabolism pathway and energy metabolism pathway to improve energy utilization. At the same time, we adjusted the balance of the rumen “core microbiota”, which was regulated to promote the development of rumen and maintain the homeostasis of rumen environment (which relies Tibetan sheep can better adapt to the harsh environment in different periods of the Qinghai-Tibet Plateau). This provides a theoretical basis for the breeding and management of Tibetan sheep on the Qinghai-Tibet Plateau.

Abstract

As an important ruminant on the Qinghai-Tibet Plateau, Tibetan sheep can maintain their population reproduction rate in the harsh high-altitude environment of low temperature and low oxygen, which relies on their special plateau adaptations mechanism that they have formed for a long time. Microbiomes (known as “second genomes”) are closely related to the nutrient absorption, adaptability, and health of the host. In this study, rumen fermentation characteristics, the microbiota, and rumen epithelial gene expression of Tibetan sheep in various months were analyzed. The results show that the rumen fermentation characteristics of Tibetan sheep differed in different months. The total SCFAs (short-chain fatty acids), acetate, propionate, and butyrate concentrations were highest in October and lowest in June. The CL (cellulase) activity was highest in February, while the ACX (acid xylanase) activity was highest in April. In addition, the diversity and abundance of rumen microbes differed in different months. Bacteroidetes (53.4%) and Firmicutes (27.4%) were the dominant phyla. Prevotella_1 and Rikenellaceae_RC9_gut_group were the dominant genera. The abundance of Prevotella_1 was highest in June (27.8%) and lowest in December (17.8%). In addition, the expression of CLAUDIN4 (Claudin-4) and ZO1 (Zonula occludens 1) was significantly higher in April than in August and December, while the expression of SGLT1 (Sodium glucose linked transporter 1) was highest in August. Correlation analysis showed that there were interactions among rumen fermentation characteristics, the microbiota, and host gene expression, mainly by adjusting the amino acid metabolism pathway and energy metabolism pathway to improve energy utilization. At the same time, we adjusted the balance of the rumen “core microbiota” to promote the development of rumen and maintain the homeostasis of rumen environment, which makes Tibetan sheep better able to adapt to the harsh environment in different periods of the Qinghai-Tibet Plateau.