A sandwich ELISA for porcine alpha-1 acid glycoprotein (pAGP, ORM-1) and further demonstration of its use to evaluate growth potential in newborn pigs

A simple, reproducible sandwich, ELISA was developed to measure porcine alpha-1 acid glycoprotein (pAGP, ORM-1) in pig plasma. Porcine AGP isolated from serum was purchased and a polyclonal antisera was prepared in rabbits using the whole pAGP molecule as immunogen. The antiserum was affinity purified, and a portion of the purified antibody fraction was labeled with horseradish peroxidase. Porcine AGP protein was used as a standard, whereas commercially available buffers and reagents were utilized throughout the assay. The assay was specific for pAGP, had a lower limit of detection of 3.2 ng/mL, and could be used to quantify pAGP in plasma or serum. Using this ELISA, we corroborated our previous findings obtained by RID assay, which demonstrated that the AGP concentration in newborn piglets is negatively associated with preweaning growth rate. The current data were obtained using piglets from a different geographical location and genetic background and showed that elevated AGP at birth was associated with reduced preweaning growth rate (P < 0.001, r = 0.433, n = 19 litters). In addition, litters with a greater average AGP at birth were at a growth disadvantage compared with litters with reduced average AGP plasma concentrations (P < 0.001, r = 0.708, n = 19 litters). Litter average plasma AGP was a better predictor of litter preweaning growth rate than average litter birth weight. The data represent further support for using perinatal AGP concentrations as a tool to identify potential slower growing pigs and as a plasma biomarker for predicting litter growth rate.