Ruminal Bacterial Diversity of Yaks (Bos Grunniens) Fed by Grazing or Indoor Regime on the Tibetan Plateau by Analysis of165 rRNAGene Libraries

From the perspective of rumen microbiome and host metabolome, revealing the effects of feeding strategies on Jersey Cows on the Tibetan Plateau

Background

Previous studies have discussed the effects of grazing and house feeding on yaks during the cold season when forage is in short supply, but there is limited information on the effects of these feeding strategies on Jersey cows introduced to the Tibetan Plateau. The objective of this study was to use genomics and metabolomics analyses to examine changes in rumen microbiology and organism metabolism of Jersey cows with different feeding strategies.

Methods

We selected 12 Jersey cows with similar body conditions and kept them for 60 days under grazing (n = 6) and house-feeding (n = 6) conditions. At the end of the experiment, samples of rumen fluid and serum were collected from Jersey cows that had been fed using different feeding strategies. The samples were analyzed for rumen fermentation parameters, rumen bacterial communities, serum antioxidant and immunological indices, and serum metabolomics. The results of the study were examined to find appropriate feeding strategies for Jersey cows during the cold season on the Tibetan plateau.

Results

The results of rumen fermentation parameters showed that concentrations of acetic acid, propionic acid, and ammonia nitrogen in the house-feeding group (Group B) were significantly higher than in the grazing group (Group G) (P < 0.05). In terms of the rumen bacterial community 16S rRNA gene, the Chao1 index was significantly higher in Group G than in Group B (P = 0.038), while observed species, Shannon and Simpson indices were not significantly different from the above-mentioned groups (P > 0.05). Beta diversity analysis revealed no significant differences in the composition of the rumen microbiota between the two groups. Analysis of serum antioxidant and immune indices showed no significant differences in total antioxidant capacity between Group G and Group B (P > 0.05), while IL-6, Ig-M , and TNF-α were significantly higher in Group G than in Group B (P < 0.05). LC-MS metabolomics analysis of serum showed that a total of 149 major serum differential metabolites were found in Group G and Group B. The differential metabolites were enriched in the metabolic pathways of biosynthesis of amino acids, protein digestion and absorption, ABC transporters, aminoacyl-tRNA biosynthesis, mineral absorption, and biosynthesis of unsaturated fatty acids. These data suggest that the house-feeding strategy is more beneficial to improve the physiological state of Jersey cows on the Tibetan Plateau during the cold season when forages are in short supply.

Dynamic alterations in yak (Bos grunniens) rumen microbiome in response to seasonal variations in diet

Rumen microorganisms play important roles in the healthy growth of yaks. This study investigated changes in yak rumen microbiome during natural grazing at the warm seasons and supplementary feeding at cold seasons. High-throughput sequencing of 16S rRNA and metagenome analysis were conducted to investigate the structures and functions of yak rumen microbial communities. The results indicated that Bacteroidetes and Firmicutes were the most abundant phyla. In addition, Bacteroidetes might play a more important role than Firmicutes during the supplementary feeding stage (spring and winter), but less during natural grazing stage (summer and autumn). KEGG analysis showed that the amino sugar and nucleotide sugar metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, starch and sucrose metabolism, and fructose and mannose metabolism were the main pathways in the microbial community, which were significantly different between seasons. The carbohydrate-active enzymes (CAZyme) annotation revealed that cellulose was an important carbon source for microorganisms in yak rumen. Glycoside hydrolases (GHs) were the most abundant class of CAZymes, followed by glycosyl transferases (GTs), which were important to digestion of oil, cellulose, and hemicellulose in food. These results contribute to the understanding of microbial components and functions in yak rumen.

Differential Effects of Natural Grazing and Feedlot Feeding on Yak Fecal Microbiota

Variation in food and diet shapes the diversity of the gut microbiota of ruminants. The present study investigated the microbial diversity in the fecal microbiota of yaks reared under natural grazing and feedlot system. A total of 48 domestic yaks with an average age of 7.5 years were selected from two different grazing habitats: one group grazed on natural pasture (grazing yaks—GY) while the other group was fed fodder and concentrate (feedlot yaks—FY). Crude protein, non-fiber carbohydrate, hemicelluloses, and digestible dry matter contents of natural pastures were higher than those in the feedlot. The lower insoluble fiber contents were found in grazing land. The 16S rRNA gene sequencing revealed 675 and 348 unique operational taxonomic units (OTUs) in the GY and FY, respectively, in addition to 1,778 common OTUs. Overall, a total of 9,891 OTUs were identified as a whole, of which 6,160 OTUs were from GY and 3,731 were from FY. Shannon index analysis revealed a higher bacterial diversity in GY than FY. At the phylum level, Firmicutes were dominant bacterial taxa in both groups. The relative abundance of Firmicutes in GY (56% ± 0.05) was higher than in FY (41% ± 0.08). At the family level, GY had a significantly higher abundance of Ruminococcaceae (p &lt; 0.001) and Rikenellaceae (p &lt; 0.001) than FY, but FY had a significantly higher abundance of Prevotellaceae than GY (p &lt; 0.001). At the genus level, abundances of Faecalibacterium, Alloprevotella, and Succinivibrio were higher in FY than in GY. This study presents novel information on fecal bacterial composition and diversity in yaks reared under two different production systems.

Microbiome and Metabolomics Reveal the Effects of Different Feeding Systems on the Growth and Ruminal Development of Yaks

The change in the feeding system can greatly improve the growth performance of the yak (Bos grunniens), an important livestock species in the plateau region. Here, we comprehensively compared the effects of different feeding systems on the growth performance and ruminal development of yaks, and investigated the effects of ruminal microorganisms and metabolites using the 16S rRNA gene sequencing and liquid chromatograph–mass spectrometer (LC-MS) technologies. We found that compared to traditional grazing feeding, house feeding significantly improved the growth performance (such as average daily gain and net meat weight) and rumen development of the yaks. At the genus level, the abundance of Rikenellaceae RC9 Gut group, Christensenellaceae R-7 group, Lachnospiraceae NK3A20 group, Ruminococcaceae UCG-014, and Prevotellaceae UCG-003 showed significant differences and was closely related to rumen development in the two distinct feeding systems. Also, metabolomics revealed that the change in the feeding system significantly affected the concentration and metabolic pathways of the related rumen metabolites. The metabolites with significant differences were significantly enriched in purine metabolism (xanthine, adenine, inosine, etc.), tyrosine metabolism (L-tyrosine, dopaquinone, etc.), phenylalanine metabolism (dihydro-3-caumaric acid, hippuric acid, etc.), and cAMP signaling pathway [acetylcholine, (-)-epinephrine, etc.]. This study scientifically support the house fattening feeding system for yaks. Also, our results provide new insights into the composition and function of microbial communities that promote ruminal development and in general growth of the yaks.

Dynamics of rumen bacterial composition of yak (Bos grunniens) in response to dietary supplements during the cold season

This study aimed to explore the rumen bacterial community of yak in response to dietary supplements during the cold season. In addition, the rumen fermentation products were also analyzed. Twenty-one female domestic yaks were randomly divided into three groups i.e., pure grazing (GG) group, grazing plus oats hay supplement (OG) group, and grazing plus concentrate supplement group (CG). Rumen contents were collected after 90 days to assess rumen fermentation parameters and bacterial community. The GC group presented higher concentrations of ammonia nitrogen (P < 0.001), and total volatile fatty acids (TVFA) (P < 0.001), and lower rumen pH (P < 0.001) compared to other experimental groups. The CG group displayed higher proportions of propionate, butyrate, isobutyrate, and isovalerate while lower A/P ratio compared to other experimental groups. Shannon, Chao1, and ACE values were significantly lower in the OG group compared to GG and CG groups. Anosim test showed significant differences in bacterial community structure between groups but the PCA plot was not very informative to see these differences. Bacteroidetes, Proteobacteria, and Firmicutes were the three dominant phyla in all groups. The genera Oscillospira was more abundant in GG and OG groups. Higher relative abundance of Ruminococcus and Clostridium was observed in the GG group, while Ruminobacter, Corynebacterium, and Selenomonas were more abundant in the CG group. These findings will help in improving our understanding of rumen bacteria in yaks in response to changes in diet.

Rumen bacteria and meat fatty acid composition of Sunit sheep reared under different feeding regimens in China

BACKGROUND

Rumen bacteria play a critical role in feed degradation and productivity. This study evaluated the impact of feeding regimen on the rumen microbial populations and fatty acid composition of the meat of sheep. Twenty-four Sunit sheep were raised on a grass pasture from birth to 9 months of age, at which time they were randomly divided into two feeding groups: pasture feeding (PF) and barn feeding (BF). Sheep in the PF group were allowed to graze freely on wild grassland for 3 months. Sheep in the BF group were confined for 3 months to a dry barn, in which they roamed freely with corn straw and corn.

RESULTS

Sheep in the PF group had greater rumen bacteria diversity. The relative abundances of the genera Butyrivibrio_2, Saccharofermentans and Succiniclasticum were increased, and that of the genus RC9_gut_group was decreased, in the PF compared to the BF sheep. The n-3 polyunsaturated fatty acid contents were greater in meat from PF sheep than from BF sheep. In addition, the α-linolenic acid (C18:3 n-3, ALA) and conjugated linoleic acid (CLA) contents were positively correlated with the abundance of Butyrivibrio_2.

CONCLUSION

Grazing may improve the diversity of rumen bacteria and increase the proportion of ALA and CLA in sheep meat. © 2020 Society of Chemical Industry.

Rumen prokaryotic communities of ruminants under different feeding paradigms on the Qinghai-Tibetan Plateau

Yak and Tibetan sheep are the major indigenous ruminants on the Qinghai-Tibetan Plateau in China. The aim of this work was to study the differences in ruminal fermentation parameters and rumen prokaryotic community composition between hosts and feeding paradigms. The 16S rRNA genes targeting bacteria and archaea were sequenced using the MiSeq platform. The results showed that the prokaryotic community structure between yak and Tibetan sheep was significantly different (P<0.01). A significant difference in structure was also found between groups of yaks barn fed with a total mixed ration (TMR) and those naturally grazing (NG) (P=0.034), as well as for Tibetan sheep of the two groups (P=0.026). The core prokaryotic populations that existed in the rumen mostly dominated the structure. There was an obvious correlation of the prokaryotic community composition at the phylum and genus levels with the host or the feeding pattern. In addition, Tibetan sheep showed significantly higher yields of volatile fatty acids (VFAs) than yak, as did the NG group compared with the TMR group. In conclusion, both the host and feeding pattern may influence rumen microbial ecology system, with host effects being more important than those of the feeding pattern.