Study on development regularity and candidate genes of spur in Huainan chicken.

This study fitted the growth curve of Huainan chicken spurs and investigated the relationships between spur growth and carcass traits as well as meat quality. It also identified central regulators affecting the growth of Huainan chicken spurs via transcriptome analysis. The study measured the spur length of 500 male Huainan chickens at 12, 16, 20, 24 and 28 weeks and three nonlinear mathematics models were used to fit the growth patterns. At 20 weeks of age, 30 male birds were selected based on spur length and divided equally into two groups: long spur length group (L) and short spur length group (S). The carcass traits and meat quality of both groups were measure. Four spur tissues were selected from each group for RNA isolation. All three nonlinear mathematics models had a high index of fitness (R2 > 0.99), with the von Bertalanffy model showing the best fit (R2 = 0.99982) for spur growth. At 20 weeks of age, there were no significant differences in carcass traits or meat quality between L group and S group. Based on differential expression gene analysis, a total of 309 differentially expressed genes (DEGs) (p < 0.05, |log2(foldchange)| > 1) were identified from the two groups. Of these, 167 genes were up-regulated and 142 genes were down-regulated in the L group. The DEGs collagen type IX alpha 1 chain (COL9A1), collagen type IX alpha 3 chain (COL9A3), Sp7 transcription factor (SP7) and pleiotrophin (PTN), which are involved in "bone mineralization", "neuroactive ligand-receptor interaction", "calcium signaling pathway", and "ECM-receptor interaction" and may play a role in the regulation of growth and development of chicken spurs. These results offer valuable information for further understanding of spur growth and development traits in chickens.