design: Blood at 5 weeks of age is collected using Laboratory-made FTA card. DNA was extracted from blood samples using magnetic bead technology. Equal amounts of Tn5ME-A/Tn5MErev and Tn5ME-B/Tn5MErev were incubated at 72  for 2 min, then were placed on ice immediately for 1 min. Tn5 was loaded with the Tn5ME-A+rev and Tn5ME-B+rev in 2 Tn5 dialysis buffer at 25 for more than 2 h. All linker oligonucleotides were same as the previous report. All libraries were sequenced on one lane or two lanes of MGISEQ-2000 to generate 2100bp paired-end reads.