Pregnancy outcomes based on pregnancy-associated glycoproteins in milk and serum during the first trimester of gestation in Holstein dairy cows

Abstract Text: Our objective was to compare pregnancy outcomes based on pregnancy-associated glycoproteins (PAGs) in milk and serum samples from cows of known pregnancy status during the first trimester of gestation. Lactating Holstein cows (n=141) were synchronized using a Double-Ovsynch protocol for first timed AI (TAI). Blood and milk samples were collected from all cows 25 and 32-d after TAI, and pregnancy status was determined 32-d after TAI using ultrasound. Pregnant cows with singletons (n=48) continued the experiment in which blood and milk samples were collected and pregnancy status was assessed weekly from 39 to 102-d after TAI. Milk samples were assayed for PAGs by AgSource Laboratories (Menomonie, WI) and serum samples were assayed for PAGs by IDEXX Laboratories (Westbrook, ME). Milk and serum assay outcomes included relative PAG levels (S-N values), and cows were classified as pregnant (PG), nonpregnant (NP), or recheck (RC) based on threshold S-N values. Sensitivity, specificity, negative predictive value, positive predictive value, accuracy for milk PAG outcomes were 88%, 87%, 92%, 83% and 88%, respectively 25 d after TAI, and 98%, 83%, 98%, 79% and 88%, respectively 32 d after TAI. These values for serum PAG outcomes were 94%, 92%, 96%, 88% and 93%, respectively, 25 d after TAI, and 100%, 88%, 100%, 83% and 92%, respectively, 32 d after TAI. Overall, 87% (48/57) of cows maintained their pregnancy until 102 d after TAI. For the milk assay, NP and RC outcomes occurred for pregnant cows 25 (11% and 36%), 46 (4% and 17%), 53 (4% and 20%), 60 (5% and 18%), and 67 (7% and 20%) d after TAI when relative PAG levels were low. For the serum assay, NP and RC outcomes occurred for pregnant cows 25 d after TAI (6% and 35%), whereas RC outcomes occurred for pregnant cows 39 (30%), 46 (46%), 53 (59%), 60 (70%), 67 (52%), 74 (28%), 81(20%) and 88 (11%) d after TAI. Relative PAG levels in both milk and serum were negatively correlated (P<0.01) with milk production in multiparous but not primiparous cows at 53 and 60 d after TAI when relative PAG levels were at their nadir. We conclude that low relative PAG levels in both milk and serum resulted in NP and RC outcomes in pregnant cows using these assays and that both parity and milk production affected relative PAG levels in milk and serum. Supported by Hatch project WIS01171

Keywords: Pregnancy Diagnosis, Pregnancy Associated Glycoprotein, Milk