title: QTL mapping of egg albumen quality in egg layers.
abstract: BACKGROUND
  A fresh, good quality egg has a firm and gelatinous albumen that anchors the yolk and restricts growth of microbiological pathogens. As the egg ages, the gel-like structure collapses, resulting in thin and runny albumen. Occasionally thin albumen is found in a fresh egg, giving the impression of a low quality product. A mapping population consisting of 1599 F2 hens from a cross between White Rock and Rhode Island Red lines was set up, to identify loci controlling albumen quality. The phenotype for albumen quality was evaluated by albumen height and in Haugh units (HU) measured on three consecutive eggs from each F2 hen at the age of 40 weeks. For the fine-mapping analysis, albumen height and HU were used simultaneously to eliminate contribution of the egg size to the phenotype.
  
  
  RESULTS
  Linkage analysis in a small population of seven half-sib families (668 F2) with 162 microsatellite markers spread across 27 chromosomes revealed two genome-wide significant regions with additive effects for HU on chromosomes 7 and Z. In addition, two putative genome-wide quantitative trait loci (QTL) regions were identified on chromosomes 4 and 26. The QTL effects ranged from 2 to 4% of the phenotypic variance. The genome-wide significant QTL regions on chromosomes 7 and Z were selected for fine-mapping in the full set composed of 16 half-sib families. In addition, their existence was confirmed by an association analysis in an independent commercial Hy-Line pure line.
  
  
  CONCLUSIONS
  We identified four chicken genomic regions that affect albumen quality. Our results also suggest that genes that affect albumen quality act both directly and indirectly through several different mechanisms. For instance, the QTL regions on both fine-mapped chromosomes 7 and Z overlapped with a previously reported QTL for eggshell quality, indicating that eggshell membranes may play a role in albumen quality.
authors: MTT Biotechnology and Food Research, Jokioinen 31600, Finland. mervi.honkatukia@mtt.fi.
authors: Mervi
authors: M
authors: Honkatukia
authors: Maria
authors: M
authors: Tuiskula-Haavisto
authors: Jesus
authors: J
authors: Arango
authors: Jonna
authors: J
authors: Tabell
authors: Matthias
authors: M
authors: Schmutz
authors: Rudolf
authors: R
authors: Preisinger
authors: Johanna
authors: J
authors: Vilkki
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics*; D002874:Chromosome Mapping; D002875:Chromosomes; D003627:Data Interpretation, Statistical; D004529:Egg White; D005260:Female; D008040:Genetic Linkage; D005819:Genetic Markers; D016678:Genome; D005838:Genotype; D018895:Microsatellite Repeats; D010047:Ovalbumin; D010058:Oviposition; D010641:Phenotype; D040641:Quantitative Trait Loci
chemical_list: D005819:Genetic Markers; D010047:Ovalbumin
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