|CAPERNA, THOMS - Retired ARS Employee
|Blomberg, Le Ann
Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2017
Publication Date: 4/8/2017
Citation: Caperna, T.J., Shannon, A.E., Stoll, M.J., Kahl, S., Blomberg, L., Vallet, J.L., Ramsay, T.G. 2017. A sandwich ELISA for porcine alpha-1acid glycoprotein (pAGP, ORM-1) and further demonstration of its use to evaluate growth potential in newborn pigs. Domestic Animal Endocrinology. 60:75-82. doi: 10.1016/j.domaniend.2017.04.001.
Interpretive Summary: Some serum proteins are involved in the response to inflammation or sickness and are described as acute phase proteins. A particular acute phase protein called alpha 1-acid glycoprotein (AGP) has unique properties in the pig. The serum concentration of AGP is extremely high in the fetal and neonatal pig and is in fact the major protein in the serum at these ages. The level of this protein very rapidly declines before weaning. Previous work by our group suggested that plasma AGP at birth might predict future growth rate to weaning, thus serve as a growth marker. The present study describes the development of a high throughput blood test that permits rapid screening of large numbers of samples from newborn animals. Secondly, this study describes a collaboration between two different ARS locations to expand this research to include larger number of animals in the evaluation of plasma AGP in newborns as a predictor of postnatal growth. Approximately 200 piglets across 19 litters of pigs were sampled following birth and plasma AGP was measured by the newly developed blood test. Analysis of the test results demonstrated that plasma AGP in the newborn is a very good predictor of preweaning growth in the individual pig. More importantly, the average plasma AGP value for all of the pigs within a litter provides a very powerful predictor of the potential growth of that litter of pigs to weaning. The cost to individually identify and treat piglets in a large scale production facility is generally unfeasible. Rather, treatment of entire litters is the reality of cost effective management in most circumstances. Thus, usage of litter average AGP to effectively identify litters at day 1 of age that will perform poorly to weaning provides a tool to target specific sows/litters for intervention within several days after birth to improve overall litter performance, animal health and well-being.
Technical Abstract: A simple, reproducible sandwich ELISA was developed to measure porcine alpha-1 acid glycoprotein (pAGP, ORM-1) in pig plasma. Pig 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. Pig AGP protein was used as a standard while 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 radial immunodiffusion RID assay, which demonstrated that the AGP level 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 higher AGP at birth was associated with lower preweaning growth rate (P < 0.001, r = 0.433, n = 19 litters). In addition, litters with a higher average AGP at birth were at a growth disadvantage compared to litters with lower 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.