Between animal variation in KEGG pathways. a) Second level KEGG assignments of sequence reads. The “microbes” samples are microbial metagenomes ; other viromes include representatives from cattle, human saliva, swine faeces and non host-associated environments [8, 18–20]. b) Principle component analysis of the second level KEGG pathways. PC1 (X axis) explains 53.1% of the variation, PC2 (Y axis) explains 13.1% of the variation.