Microsatellite markers may be ineffective in selection of laying hens for polygenic production traits.

Previous research on mapping QTL in a reference family of laying hens indicated that 5 microsatellite loci (MCW0133, MCW0170, MCW0114, MCW0139, and LEI0074) were significantly associated with genome regions affecting shell strength as well as egg and yolk weights. The aim of our investigation was to verify if those markers could be useful in selection of laying hens. The study involved 2 breeds of randomly segregating populations: Rhode Island Reds selected divergently and Green-legged Partridgenous chickens selected upwardly, over 4 generations, for the mentioned egg quality traits. The influence of marker genotype on bird performance was assessed through the prediction of breeding values using a model that distinguished the marker effect from that of the polygenic effect and by comparing breeding values between different genotypes at given marker loci. The effects of the linked QTL regions appeared too small to significantly differentiate the outcomes of classifications fitting or not fitting the marker genotype. Comparison of breeding values between microsatellite genotypes for laying and egg traits revealed that antagonistic pleiotropic effects exist between these 2 groups of traits, adding to the difficulty of accounting for marker genotypes in the selection of laying hens.