Induced PG release alters steroid concentrations but not pregnancy survival in cows

Abstract Embryonic mortality (EM) is a major factor limiting reproductive efficiency in cattle and, despite negative connotations related to reproductive performance, prostaglandin F2α (PGF2α) is capable of being released by the uterus by day 30 of gestation. Therefore, the objective was to evaluate differences in PGF2α release following an oxytocin challenge between cows with high circulating concentrations of pregnancy associated glycoproteins (PAG) vs low PAG, due to association of increased PAG concentrations with pregnancy success. At day 30 of gestation, pregnant cows were divided into oxytocin treatment (OT; n = 13) and control (CON; n = 12) groups. Treatment cows were further subdivided by circulating PAG concentration (High PAG, n = 7; Low PAG, n = 6). Blood samples were collected every 30 minutes beginning 1 hour before oxytocin administration and continuing for 4 hours. Prostaglandin F2α metabolite (PGFM), progesterone, estradiol-17β (E2) and PAG concentrations were quantified. Peak concentration of PGFM occurred 2 hours after oxytocin injection in treatment animals and returned to baseline levels by 4 hours. No correlations were observed between PAG and PGFM, progesterone or E2 concentrations (P > 0.05). There was no difference in initial or final PGFM concentrations between groups (P > 0.05). Progesterone and E2 concentrations decreased in cows following treatment of oxytocin (P