Detection of pregnancy-associated glycoproteins (PAGs) in prolific and non prolific ewes from early to late gestation and postpartum

Pregnancy-associated glycoproteins (PAGs) are placental antigens that were initially characterized as pregnancy markers in the maternal circulation of bovine species (Zoli et al., 1992, Biol. Reprod. 46: 83-92). After that, the measurement of such molecules in maternal blood as a method for pregnancy diagnosis in other ruminants has been demonstrated in several species. It can give useful information to develop appropriate feeding strategies for pregnant females and to assure requirements of the mother and the growing of fetuses and to avoid metabolic disorder associated to pregnancy. The aim of the present study was to investigate the use of a PAG ELISA-Sandwich kit (Ref. code E.G.7. CER. Marloie, Belgium) vs two homologous radio-immunoassay described in El Amiri et al. (2007; Reprod. Domest. Anim. 42:257-62) to detect PAGs in blood samples collected from Boujaâd (non prolific, n=8) and Boujaâd x D’man (prolific, n=20) sheep from early to late gestation and postpartum. Ewes were assumed to be pregnant when PAG concentrations were higher than 0.8 ng/ml in ELISA and 0.3 in RIAs. In addition the samples were also explored by the double immunodiffusion radial (El Amiri et al., 2003, Theriogenology. 59:1291- 301) after PAG extractions. The results show that in both systems (ELISA vs RIAs), the PAG concentrations were significantly lower in Boujaâd a non prolific sheep than in Boujaâd x D’man a prolific sheep. Furtemore, the concentrations in RIAs were 3 folds higher than those in ELISA. In all systems, the concentrations decreased rapidly after lambing (21 weeks) reaching basal values at fourth week postpartum in ELISA vs RIAs. In ELISA all pregnant females showed PAGs level above 1.4 ng/ml from day 24. The double radial immunodiffusion showed positive reactions in ewes carrying more dead fetus. In conclusion, the plasma PAG investigated in the present study showed that the ELISA technique is proved to be a convenient and reliable means for early pregnancy diagnosis as well as for pregnancy fellow up in sheep. From 24 days of gestation, its reliability achieved 100% and, therefore, matches conventional approaches of pregnancy detection. The PAGs could also be detected after extraction from plasma of pregnant ewes using the double radial immunodiffusion. However, for using this technique in routine, further studies are necessary.