Circulating nucleic acid extraction was performed in triplicate from the sera of P (N = 12) and NP (N = 16) dairy cows. DNA concentration was measured in a microplate reader GENios Pro (Tecan) using Quant-iT dsDNA assay (Invitrogen). DNA samples were diluted to a final concentration of 1 pg/μL. We collected the serum samples and performed the CNA extraction as described in section 2.2. “DNA extraction and whole genome amplification.” After extraction and diluting the nucleic acids, we directly performed the qPCR assays using pure CNAs as templates.