Use of Pregnancy Associated Glycoproteins to Determine Fetal Age Throughout Gestation in Cattle

Objective The objective of the current study was to determine if a commercially available blood pregnancy test could be modified to detect differences in pregnancy-associated glycoprotein (PAG) concentrations to indicate stage of pregnancy or fetal age in cattle. Study Description Previously identified pregnant females were grouped by age (pre-primiparous or multiparous). Blood samples were collected between day 27 and 190 of pregnancy (n = 176 from pre-primiparous and n = 240 from multiparous) and serum was tested in duplicate using a commercially available blood pregnancy test, IDEXX Alertys Pregnancy Test. Procedures were adapted to allow concentrations to fall within the detectible range of the assay. Animals were grouped by parity (pre-primiparous vs multiparous) into 4 gestational groups (group 1 - < 30 days, group 2 - 30 to 90 days, group 3 - 91 to 178 days, and group 4 - >178 days). Data were analyzed using the MIXED procedure of SAS with parity and gestational age in the model. There was an effect of parity, gestational age, and a parity by gestational age interaction (P < 0.01). Pre-primiparous animals had greater concentrations of PAGs compared to multiparous animals. Among pre-primiparous animals, serum PAG concentrations did not differ between gestational age groups 1, 2, or 3 (P > 0.37), but group 4 had greater PAG concentrations than all other groups (P < 0.01). Among multiparous animals, serum PAG concentrations decreased from group 1 to 2 (P < 0.01), and then increased throughout gestation (P < 0.01). Data were then analyzed using the REG procedure in SAS within gestational age group. There was a positive correlation between gestational age and PAG concentrations among both pre-primiparous (P < 0.01; R2 = 0.25) and multiparous (gestational age 30 and greater P < 0.01; R2 = 0.64).