Cytogenetic study of early chicken embryos: effect of naked neck gene and high ambient temperature.

High ambient temperature (> 30 C) decreases fertility of breeder hens, but this effect has been shown to be greatly reduced in females carrying the naked neck gene (Na). Sixty-four females each of the three different genotypes, Na/Na (homozygous naked neck), Na/na+ (heterozygous), and na+/na+ (normally feathered), were equally distributed in two climate control rooms with individual cages, at a constant temperature of either 22 C or 31 C. Five hundred and seventy-six embryos were examined after 16 to 18 h of incubation for karyological analyses. Abnormalities consisted of diploid-haploid and diploid-triploid chimeras. The frequency of chimeric embryos was significantly affected by dam genotype. Naked neck females showed a much lower proportion of abnormal embryos than normally feathered females whatever the temperature. The highest proportion of chimeras was observed for the na+/na+ dams maintained at 31 C. However, the effect of temperature was not generally significant.