According to Mendelian heredity laws, the sex ratio of a given chicken population during hatching is expected to be 1:1. In this study, we collected 432 chicken embryos that died during the first week of incubation from 5 different breeds. The sexes of the early-dead embryos were determined by using the previously described molecular sexing technique of double PCR. The female-to-male sex ratio was analyzed for departure from the expected 1:1 sex ratio by chi(2) testing. These results showed that the number of female dead embryos was significantly greater than that of males in the Hubei local breeding stock, Zhusi, and Hy-line Variety Brown (P < 0.05, P < 0.01, P < 0.01 respectively), with observed female-to-male sex ratios of 1.40:1, 2.03:1, and 2.22:1, respectively. Two other Chinese local breeds (the Yellow chicken and the Aijiaohuang chicken) also showed altered sex ratios, although the differences were not significant. Altogether, these results indicated that female chickens were more likely than male chickens to die at the early stages of incubation.

No abstract

To investigate the effect of a factor-associated suicide (FAS) gene polymorphism on the death of chicken embryos, we genotyped 190 dead embryos and 69 normally developing embryos from 7200 hatching Short-Leg Yellow Chicken eggs, as well as 119 dead embryos and 69 normally developing embryos from 4650 hatching Yellow B Chicken eggs. The results showed that there were significant (P < 0.05) genotypic differences between dead and normally developing embryos for this FAS gene polymorphism, a SNP in exon 3 (NC_006093.2:g.6514A>C, rs15793179). Logistic regression revealed that Short-Leg Yellow Chicken embryos with genotype g.6514CC had a significantly (P < 0.01) higher risk of death than those with genotype g.6514AC. This polymorphism has the potential to be an effective tool when used in conjunction with traditional selection methods.