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Summary Body size traits reflect the condition of body development, are always mentioned when a breed is described, and are also targets in breeding programmes. In chicken, there are several reports focused on body size traits, such as shank length, tibia length or bone traits. However, no study was carried out on chest width (CW), chest depth (CD), body slope length (BL) and head width (HW) traits. In this study, genome scans were conducted on an F2 resource population (238 F2 individuals from 15 full-sib families derived from an intercross of the White Plymouth Rock with the Silkies Fowl) to identify quantitative trait loci (QTL) associated with CW, CD, BL and HW from 7 to 12 weeks of age. In total, 21 significant or suggestive QTL were found that affected four body size traits. Four QTL reached 1% genome-wide significance level: at 297 cM on GGA3 (associated with CW at 9 weeks of age), between 155 and 184 cM on GGA1 (affecting BL traits at 9 and 10 weeks of age), at 22 cM on GGA2 (related with BL traits at 12 weeks of age) and at 36 cM on GGA1 (for HW trait at 8 weeks of age). [ABSTRACT FROM AUTHOR]

Two sequence variants of the aldolase C ( ALDOC) gene were discovered based on comparison of the sequences from an altiplano chicken breed (Tibetan chicken) and two lowland breeds (White Leghorn and ShouGuang). Gel-shift results indicated that one of these variants, L25375:c.310-258G>A, was able to bind hypoxia-induced factor-l (HIF1A), therefore, functioning as a hypoxia response element (HRE). The combined activity of the HRE and HIF1A could increase under the influence of a hypoxic stimulus. Hypoxia leads to increased death rates of chicken embryos, while the L25375:c.310-258G>A described herein is prevalent in healthy embryos grown under hypoxic conditions. Fluorescence quantitative real-time PCR results revealed that HIF1A upregulated the transcript level of the glycolytic enzyme ALDOC in the brain and skeletal muscle of animals subjected to hypoxia. Thus, a large amount of ATP is produced by increased glycolysis, allowing the organism to meet energy metabolism demands. As such, we believe this sequence variant is an adaptation to external anoxic environment. [ABSTRACT FROM AUTHOR]