## 3 Results and Discussion
### Effects of Characteristic Bioactive Metabolites on Meat Quality Traits  
The meat quality traits of 30 Silkie chickens and 30 Wuding chickens are shown in Table 1. In Silkie chickens, the values of pH24h and shear force were higher (_p_ < 0.05), and the pressing loss, cooking loss, and meat color \(L^{*}\) and \(b^{*}\) values were lower (_p_ < 0.05). The lower pressing loss and cooking loss indicate that their water-holding capacity was better. Electronic tongue analysis showed that the sensory values of umami, richness, and bitterness were higher than the tasteless point (0) in both Silkie and Wuding chickens, indicating that they could be detected by taste buds. The umami value in the breast muscle of Silkie chickens was higher (_p_ < 0.05, Table 2). We explored the effects of characteristic bioactive metabolites on meat quality traits in Silkie chickens (Figure 3 and Table S5). Correlation analysis showed that melanin was positively correlated with shear force, which may be due to the high melanin content in collagen of Silkie chickens, increasing the toughness of collagen [48] and the shear \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Silkie Chickens** & **Wuding Chickens** & _p Value_ \\ \hline pH24h & \(5.75\pm 0.28\)a  & 5.45 \(\pm\) 0.29b  & 0.01 \\ \(L^{*}\)24h & 48.83 \(\pm\) 2.16b  & 59.40 \(\pm\) 3.30a  & \textless{}0.001 \\ \(a^{*}\)24h & 3.00 \(\pm\) 1.21 & 2.57 \(\pm\) 1.53 & \\ \(b^{*}\)24h & 5.24 \(\pm\) 1.96b  & 8.19 \(\pm\) 2.92a  & \textless{}0.001 \\ Pressing loss (\%) & 7.30 \(\pm\) 1.51b  & 8.31 \(\pm\) 1.88a  & 0.02 \\ Cooking loss (\%) & 13.95 \(\pm\) 1.61b  & 15.19 \(\pm\) 2.22a  & 0.02 \\ Shear force (kg) & 3.62 \(\pm\) 0.93a  & 3.15 \(\pm\) 0.58b  & \textless{}0.001 \\ Melanin content (ng/g) & 439.72 \(\pm\) 337.85a  & 0.00 \(\pm\) 0.00b  & \textless{}0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Meat quality traits in Silkie and Wuding chickens. force [49]. Adenosine 5\({}^{\prime}\)-monophosphate (AMP) showed a positive correlation with pH\({}_{\text{24h}}\) and a negative correlation with the \(L^{\star}\) value. One study showed that the pH value of duck breast muscle was significantly increased (\(p<0.05\)) and the \(L^{\star}\) value was significantly decreased (\(p<0.05\)) after AMP treatment [50]. Biotin content was negatively correlated with the \(L^{\star}\) value. One study showed that addition of biotin to the diet resulted in a lower \(L^{\star}\) value of pig loin muscle [51]. Creatine showed negative correlations with the \(L^{\star}\) value and pressing loss. Previous studies have showed that increased the creatine content in muscle could postpone the pH decline after slaughter and improve the water-holding capacity [52; 53]. The nicotinic acid content was negatively correlated with the \(L^{\star}\) value. One study showed that dietary nicotinic acid supplementation linearly decreased (\(p<0.05\)) the \(L^{\star}\) value in the breast muscle of Wulong geese [54]. Umami taste showed positive correlations with AMP, guanine, and UMP levels. Previous studies showed that AMP [55], guanine [56], and UMP [57] could all enhance the umami taste of meat. Therefore, the characteristic bioactive metabolites in Silkie chickens not only exhibited health-related functions, but also improved water-holding capacity and umami taste in breast muscle. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Silkie Chickens** & **Wuding Chickens** & \(p\) **Value** \\ \hline Umami & \(8.52\pm 0.51\)1  & \(8.02\pm 0.49\)2  & \(<0.01\) \\ Richness & \(5.39\pm 0.43\) & \(5.32\pm 0.48\) & \\ Bitterness & \(1.90\pm 0.58\) & \(1.79\pm 0.58\) & \\ Aftertaste-B & \(-0.26\pm 0.16\) & \(-0.33\pm 0.23\) & \\ Astingency & \(-3.97\pm 0.36\)2  & \(-3.68\pm 0.32\)3  & \(0.01\) \\ Aftertaste-A & \(0.004\pm 0.03\) & \(-0.01\pm-0.01\) & \\ Saltiness & \(-12.10\pm 0.50\) & \(-12.22\pm 0.52\) & \\ Sourness & \(-21.73\pm 1.78\)2  & \(-19.90\pm 1.66\)3  & \(<0.01\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Electronic tongue analysis in Silkie and Wuding chickens.