Pools of 70 animals were snap frozen. Total RNA was extracted using a TRIzol based method using a starting volume of 500 μL. DNse was carried out using a DNse-I kit from Promega. Per sample, 1 μg of RNA was used for RNAseq library preparation, and 150bp paired-end sequencing was done on a NovaSeq600 with a sequencing depth of 10 million reads per sample by Macrogen (Amsterdam, the Netherlands).