Table 1.

Primary archaeal taxa in the pig gut.

Study number	Archaea taxa	Breeds	Age (day)	Technology	Citation
1	Methanobrevibacter (46%)	Duroc × Landrace × Yorkshire	Not given	16S rRNA sequencing	Borrel et al. (2020)
2	141 sequences (37%) related to Methanobrevibacter gottschalkii and Methanobrevibacter millerae 111 sequences (29%) related to Methanobrevibacter smithii	Erhualian × Landrace	40,50,70,330 ~ 360	16S rRNA sequencing	Liu et al. (2008)
4	Methanomicrobia and Thermococci account for 1% of the total rRNA sequences	Yorkshire	180	Metagenomic sequencing	Luo et al. (2012)
5	Across all reads, 99.91% were identified as class Methanobacteria	Meishan × Yorkshire	1,3,7,14	16S rRNA sequencing	Yong et al. (2014)
6	Euryarchaeota was the most abundance phylum Methanobacteriaceae, Methanosarcinaceae, and Candidatus Methanomethylophilaceae were the most abundant families Methanobrevibacter smithii was the most abundance species	Large White	14,21,28	Shotgun metagenomic sequencing	Quince et al. (2017)
7	Methanobrevibacter (23.02%) Candidatus methanomethylophilus (10.52%)	17 breeds from 11farms	Not given	Shotgun metagenomic sequencing	Sharpton (2014)
8	Methanobrevibacter A (0.23% of the total rRNA sequences) Methanobrevibacter (0.067% of the total rRNA sequences) Methanomethylophilus (0.062% of the total rRNA sequences) and Methanosphaera (0.023% of the total rRNA sequences)	Not given	7, 14, 21, 28, 35, 70, and 140	Shotgun metagenomic sequencing	Xiong et al. (2022)
10	Methanobacteriaceae family reaching 98.1% Methanomassiliicoccales reaching 1.8%	Landrace × Large White	28	16S rRNA sequencing	Deng et al. (2022)