Genetic Analysis And The Associated Molecular Markers Of The Egg Quality Traits In Dwarf Layers

Egg quality traits of 901 hens from a pureline of dwaf layers were measured at the age of 40 weeks, including egg weight (EW), Haugh Unit (HU), shell strength (SS), shell color (SC), shell thickness (ST), egg shape index (SI) and yolk color (YC). Tail analysis was conducted to screen possible genetic markers associated with egg quality traits. Five percent individuals at each tail of the whole population were selected to establish two extrem groups for Haugh Unit and shell strength, and standard selective genotyping were performed. Microsatellite primers of 25 pairs in total have been employed to perform electrophoresis to determine the genotype of individual. The result is as following:The means for EW, HU, SS, SC, ST, SI and YC were 53.80g, 86.40, 3.3kg/cm2, 41.78, 342.90um, 1.40 and 6.8 respectively. MTDFREML package was used to estimate heritability (h2) of the traits above, with the results being 0.52, 0.46, 0.38, 0.43, 0.23, 0.11 and 0.16 respectively. The means of polymorphic information content (PIC) and heterozygosity (H) of 17 markers on the autosome were 0.441 and 0.497. It is concluded that the pureline of dwarf layers had a high degree of homozygosity after selective breeding for ten years.The molecular genetic markers that are related to HU and SS were detected with tail analysis and the effect of each locus alleles were analyzed. The markers related to HU at 40 40 weeks was ADL0176 on Chromosome 2. However, only A and D among alleles A,B,C and D of ADL0176 had significant effect on HU. The allele A had negative effect while B had positive effect. Both MCW0191 and ADL0260 on Chromosome 4 had three alleles (A, B, C). The allele A of MCW0191 had positive effect on HU and allele B and C of ADL0260 had negative and positive effect on HU respectively. The allele D of all four alleles (A, B, C, D) which belong to locus LE0I0229 on Chromosome Z had positive effect on SS.