Early pregnancy diagnosis in goats by determination of pregnancy-associated glycoprotein concentrations in plasma samples

Different RIA systems available for measuring the concentrations of pregnan cy-associated glycoproteins (PAGs) in dairy goats were compared in order to evaluate their accuracy in early pregnancy diagnosis. Plasma concentration s of PAGs were determined by 3 heterologous RIA systems with a bovine PAG s tandard and tracer in combination with antisera anti-ovine PAG (RIA 1), ant i-caprine PAG(55+62) (RIA 2), anti-caprine PAG(55+59) (RIA 3), and by 2 hom ologous RIA systems that employed caprine PAG(55+62) and caprine PAG(55+59) and their specific antisera (RIAs 4 and 5, respectively). In all of the RI As, the mean concentrations of PAGs were significantly higher (P<0.01) in p regnant than in nonpregnant goats from Day 21 onwards after breeding. On Da y 21, the accuracy rates of early pregnancy diagnoses were 56% (RIA 1), 96% (RIA 2), 99% (RIA 3), 95% (RIA 4) and 90% (RIA 5), whereas on Day 28 these rates were >99% for RIAs 2, 3, 4 and 5. The RIAs for PAGs depend on protei ns from the placenta being present in maternal plasma and require only a si ngle sample of blood, to distinguish pregnant goats from those that fail to return to estrus for other reasons. The homologous and semi-heterologous a ssays are highly accurate as early as Day 21 of pregnancy. (C) 1999 by Else vier Science Inc.