(175) Circulating Pregnancy-Associated Glycoproteins are greater in primiparous and cows pregnant with male fetuses

Hunter Haberman1, Riley Puck1, Kendal Green1, Silvio Isler12, Jessica Nora Drum1 

1. 
   

   Department of Animal Science, South Dakota State University, Brookings, South Dakota
   

Pregnancy Associated Glycoproteins (PAGs) are molecules released by the embryo during the early stages of gestation. They become detectable in maternal blood around the time of attachment close to day 25. Variations in PAGs concentrations have been associated with pregnancy loss, sire, and parity. However, little is known about how the sex of the fetus would affect these concentrations. The objective of this study was to evaluate the concentrations of circulating PAGs in pregnant beef cows comparing pregnancies between male and female fetuses. Angus and Angus cross cows (n = 233 pregnancies; male n = 119; female n = 114), 4.3 years old on average (primiparous = 62; multiparous = 171) from two different farms were synchronized using a common synchronization protocol and artificially inseminated (AI) after heat detection. P</span>regnancy diagnostics (PD) was performed using ultrasonography on average at 35 days after AI (farm 1, 37d; farm 2, 32d; PD1) The cows underwent ultrasonography again at 72 days after AI on average (farm 1, 61d; farm 2, 83d; PD2), to confirm pregnancy status. Blood samples were collected from pregnant cows at both PDs. Fetal sex was determined by observing the location of the genital tubercle using ultrasonography by a single trained technician. Cows were retrospectively divided into groups based on the sex of the fetus. Plasma PAGs concentrations were analyzed using the IDEXX Rapid Visual Pregnancy Test (IDEXX Laboratories, ME) for about a half of the samples. Concentrations were estimated based on the absorbances obtained from a microplate reader according to the manufacturer's instructions. Final values were determined by calculating the difference between absorbances measured at 650 nm and 450 nm for all samples and subtracting by the negative control (Sample – Negative). Statistical analysis was performed using the MIXED procedure of SAS 9.4. Pregnancies from male fetuses had greater PAGs concentration when compared to females regardless of day or parity (Male: 2.23 ± 0.65, n = 61; Female: 2.03 ± 0.66, n = 50; P = 0.013). There was also a significant increase in overall concentration on the PD2 when compared to PD1 (n = 111; PD1 = 2.39 ± 0.53; PD2 = 2.87 ± 0.68; P = 0.0001). Parity also demonstrated and effect on PAGs concentration (P = 0.0095) with Primiparous cows being higher than multiparous (2.29 ± 0.87, n = 38 vs 2.06 ± 0.69, n = 73; respectively). In addition, these preliminary data showed a numerical difference within sex*time interaction (P = 0.15), with males being higher than females in both days (PD1_Male, n = 61, 2.44 ± 0.54, PD1_Female, n = 50, 2.33 ± 0.52; PD2_male, 2.02 ± 0.68, female 1.72±0.65). In summary, our data reveals that male fetuses may release higher concentrations of PAGs into the maternal bloodstream than their female counterparts. These findings strongly suggest that the sex of the fetus plays a significant role in the production and release of PAGs. 

Keywords: Fetal Sex, Beef cattle, Gestation, PAGs