This data set contains information on the rumen microbiome of 340 dairy cows, sequenced within the METALGEN project (RTA2015-00022-C03).-- Sequenced with a MinION from Oxford Nanopore Technology., The purpose of this data set is to serve as a training exercise to predict a complex phenotype using metagenomic data within the workshop SUPREMET 2019 "Supercomputación para la predicción de enfermedades y caracteres complejos usando información del metagenoma"., METALGEN, Ministerio de Ciencia, Innovación y Universidades, RTA2015-00022-C03., Peer reviewed