Abstract
This study was performed to investigate the initial colonization of metabolically active methanogens and subsequent changes in four fractions: the rumen solid-phase (RS), liquid-phase (RL), protozoa-associated (RP), and epithelium-associated (RE) from 1 to 60 d after birth, and manipulate methanogen community by early weaning on 40 d and supplementing rhubarb from 40 to 60 d in black goats. The RNA-based real-time quantitative PCR and 16S rRNA amplicon sequencing were employed to indicate the metabolically active methanogens. Results showed that active methanogens colonized in RL and RE on 1 d after birth. RP and RE contained the highest and lowest density of methanogens, respectively. Methanobrevibacter, Candidatus Methanomethylophilus, and Methanosphaera were the top three genera. The methanogen communities before weaning differed from those post weaning and the structure of the methanogen community in RE was distinct from those in the other three fractions. The discrepancies in the distribution of methanogens across four fractions, and various fluctuations in abundances among four fractions according to age were observed. The addition of rhubarb significantly (P < 0.05) reduced the abundances of Methanimicrococcus spp. in four fractions on 50 d, but did not change the methanogen community composition on 60 d.
Highlights
The rumen accommodates various prokaryotic and eukaryotic microorganisms that symbiotically degrade and ferment the feed ingested by the host ruminant[1]
Using real-time quantitative PCR (qPCR), the existence of metabolically active methanogens (Methanomicrobiales mobile, Methanoccocales votae, and Methanobrevibacter spp.) was observed in the rumen of calves 20 minutes after birth[8], and the presence of methanogenic archaea was found in the rumen of goats at 0 d9
Results of real-time qPCR revealed that metabolically active methanogens initially colonized rumen both in RL and RE on the first day after birth, and this is supported by the findings of Jiao et al.[9]
Summary
The rumen accommodates various prokaryotic (bacteria and archaea) and eukaryotic (protozoa and fungi) microorganisms that symbiotically degrade and ferment the feed ingested by the host ruminant[1]. It has been found that the early dietary experiences of the animal can have a greater and more lasting effect than those occurring later in life[11] This would possibly allow the manipulation of the rumen microbial community at the early period of rumen development, i.e., microbial programming[12]. Further studies[4, 14] implied that it would be possible to promote the establishment of different microbial populations in the rumen of the young animal by controlling feed management in early life. Previous in vitro and in vivo investigations found that rhubarb could inhibit ruminal methanognesis, and alter rumen fermentation through propionate production[26, 27]. RNA-based techniques could help obtain insights into the metabolic state of microbes and could be used to indicate the most active rumen microorganisms and their metabolic potential[33, 34]
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