ABSTRACT: We applied a new computational approach to predict specie-specific and conserved miRNAs, than experimentally confirmed by a modified RNA-primed Array-based Klenow Extension (RAKE) method. We identified 489 conserved and 1,178 pig-specific novel miRNAs increasing our tally of confirmed miRNAs to 1,667 novel miRNAs. In addition, RAKE allowed the identification of miRNA isoforms (isomiRs) that we demonstrated to be differentially expressed across tissues suggesting that subtle variability in isomiR expression is regulated and biologically meaningful. 90K microarray was hybridized with a pool of small RNAs from 20 different tissues (superior vena cava, adipose tissue, lung, spleen, stomach, liver, intestine, kidney, descending aorta, left atrium, left ventricle, skeletal muscle, pulmonary aorta, skin, tongue, ascending aorta, arterial white cells blood, venal white cells blood, coronary valve, lymph node). Same experiment was replicated four times to grant the reliability of the identified 3M-bM-^@M-^Y end of miRNAs and microarray slides were scanned three times at low, medium and high PMT to improve microarray dynamic range.