Abstract
BackgroundTibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai–Tibetan Plateau, China. Rumen methanogen and protozoal communities of plateau sheep are affected by their hosts and living environments, and play important roles in ruminant nutrition and greenhouse gas production. However, the characteristics, differences, and associations of these communities remain largely uncharacterized.ResultsThe rumen methanogen and protozoal communities of plateau sheep were investigated by 16S/18S rRNA gene clone libraries. The predominant methanogen order in both sheep species was Methanobacteriales followed by Methanomassiliicoccales, which is consistent with those seen in global ruminants. However, the most dominant species was Methanobrevibacter millerae rather than Methanobrevibacter gottschalkii seen in most ruminants. Compared with GS and other ruminants, TS have more exclusive operational taxonomic units and a lower proportion (64.5%) of Methanobrevibacter. The protozoa were divided into Entodiniomorphida and Vestibuliferida, including nine genera and 15 species. The proportion of holotrich protozoa was much lower (1.1%) in TS than ordinary sheep. The most predominant genus was Entodinium (70.0%) in TS and Enoploplastron (48.8%) in GS, while the most common species was Entodinium furca monolobum (43.9%) and Enoploplastron triloricatum (45.0%) in TS and GS, respectively; Entodinium longinucleatum (22.8%) was only observed in TS. LIBSHUFF analysis indicated that the methanogen communities of TS were significantly different from those of GS, but no significant differences were found in protozoal communities.ConclusionPlateau sheep have coevolved with unique rumen methanogen and protozoal communities to adapt to harsh plateau environments. Moreover, the host appears to have a greater influence on rumen methanogen communities than on rumen protozoal communities. The observed associations of methanogens and protozoa, together with the findings of previous studies on methane emissions from ruminant livestock, revealed that the lower proportion of Methanobrevibacter and holotrich protozoa may be responsible for the lower methane emission of TS. These findings facilitate our understanding of the rumen microbial ecosystem in plateau sheep, and could help the development of new strategies to manipulate rumen microbes to improve productivity and reduce the emission of greenhouse gases.
Highlights
Tibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai–Tibetan Plateau, China
Methanogen 16S rRNA and protozoal 18S rRNA gene libraries from TS and GS A total of 138 clones were obtained from the TS methanogen 16S rRNA gene (TM) library, revealing 62 unique sequences that were assigned to 28 Operational taxonomic units (OTU) based on the 98% identity criterion (Table 1)
The GS methanogen 16S rRNA gene (GM) library had 155 clones with 65 unique sequences assigned to 18 OTUs (Table 1)
Summary
Tibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai–Tibetan Plateau, China. Rumen methanogen and protozoal communities of plateau sheep are affected by their hosts and living environments, and play important roles in ruminant nutrition and greenhouse gas production. The rumen is crucial for feed digestion and energy supply in ruminants. It contains a complex microbial ecosystem including bacteria, methanogens, protozoa, fungi, and bacteriophages. These different types of symbiotic microorganisms interact with one another and affect the host’s digestion and performance. During microbial fermentation and feed energy utilization, methane (CH4) is produced as a by-product of methanogenesis by methanogens belonging to the archaeal phylum Euryarchaeota. Mitigating CH4 released by ruminants would benefit the environment and may increase the efficiency of livestock production
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