Detection of pregnancy-associated glycoproteins in milk and blood as a test for early pregnancy in dairy cows

The objective of our study was to evaluate 2 pregnancy-associated glycoprotein (PAG)-based enzyme-linked immunosorbent assays (ELISAs) for use with either blood or milk. From 12 dairy farms, 116 Montbéliarde or Holstein cows were selected that had either undergone artificial insemination (AI; n = 102) or had calved (n = 14) 2–3 months earlier and had not undergone any further AI. Serum, plasma, and milk were obtained from all cows; serum and plasma were analyzed using the blood pregnancy test and milk using the milk pregnancy test. No false-positive results were observed when samples of the 14 noninseminated cows were tested. Cows undergoing AI were sampled at ~16, 30, and 41 days post-AI. An additional milk sample was taken at ~53 days post-AI. To establish whether the inseminated cows were pregnant, the cows were subjected to transrectal ultrasonography (TU) on or around day 41. Of the 102 inseminated cows, 63 were confirmed pregnant by TU. By day 30, the serum, plasma, and milk ELISAs demonstrated 100%, 100%, and 98.1% sensitivity and 88.6%, 88.9%, and 90.3% specificity, respectively, with potential pregnancy losses 30–41 days post-AI. Accuracy obtained on serum, plasma, and milk at ~41 days post-AI and on milk at ~53 days post-AI ranged from 97.4% to 100%. There were no differences of practical significance in performance between the blood and milk ELISAs for the sampling dates chosen. This new diagnostic capability with milk samples offers a major improvement in bovine reproductive management.