Association of serum protein levels with egg productivity in Taiwan red-feathered country chickens

This study investigated the relationship between serum protein levels and egg productivity in Taiwan red-feathered country chickens (TRFCC). The total egg numbers of TRFCC (n = 157) were recorded from 25 to 48 weeks of age. Serum samples were collected at 24 and 35 weeks of age, then classified by total egg number into four groups according to mean ± 1S.D. Serum X protein levels were evaluated by protein chip technology and with an insulin-like growth factor-I (IGF-I) immunoassay. Other serum proteins (apolipoprotein A-I, ovotransferrin and vitellogenin) were found at different levels between the most productive and the least productive groups of TRFCC, were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and were quantified by age. The results showed that levels of vitellogenin were positively correlated with total egg number at 24 and at 35 weeks old (p < 0.01). Levels of apolipoprotein A-I and an IGF-1-related marker (termed X protein) in serum at 35 weeks old were correlated with total egg number (p < 0.01). Serum ovotransferrin levels remained constant regardless of total egg number. To investigate the concentration differences among the four groups of TRFCC, serum protein levels of each group were analyzed by one-way ANOVA. The results showed that those protein levels, except for ovotransferrin, in the least productive group significantly differed from the other three groups (p < 0.05). Although the correlation between those protein levels and the total egg number was not significant at the time of initial egg production, the selection strategy of those protein levels at later stages of egg production should provide a screening model to improve selection.