Extraction and quantification by ELISA of eggshell organic matrix proteins(ovocleidin-17, ovalbumin, ovotransferrin) in shell from young and old hens

The eggshell matrix is mainly composed of proteins that are thought to infl uence shell formation and calcification and, thus, modify the resulting pro perties of the shell. We investigated the potential of some of these protei ns as biomarkers of eggshell quality by developing a competitive indirect E LISA for quantifying ovotransferrin, ovalbumin, and ovocleidin-17 in eggshe ll extract. Eggshell fragments were demineralized in acetic acid (20%) and freeze-dried. The micro-extraction yield was markedly increased (>50%) when Tween 20 was added to the subsequent extraction and dialysis milieus. Micr oplates were coated with ovotransferrin and ovalbumin in a 0.1M carbonate-b icarbonate buffer, but ovocleidin-17 was fixed with acetone (-20 C, 20 min) . Optimal dilutions of the monoclonal (ovotransferrin) and polyclonal (oval bumin and ovocleidin-17) antibodies were 1/3,000, 1/25,000 and 1/4,000, res pectively. The inhibition curves were optimized by preincubating the antibo dies and proteins overnight. The intraassay coefficient (<5%), parallelism of the standards and samples curves, and recovery (101%) were satisfactory for ovotransferrin. Measurements of ovalbumin were less precise because of higher interassay variation and differences between the slopes of standard and sample inhibition curves. Ovocleidin-17 assays showed similar slopes fo r standard and eggshell extracts. Although the total protein in soluble mat rix extracts was not affected by age, the concentrations of these proteins were higher in eggshell extracts from older hens compared with those from y oung hens: 1.98x for ovotransferrin, 1.86x for ovalbumin, and 1.58x for ovo cleidin-17. The quantification of specific eggshell matrix proteins in shel l of differing quality is, therefore, a promising tool for analyzing the or igin of eggshell faults and may provide useful information for breeding pro grams.